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\section{Analysis of New Bones}  BC\_18.88-0.09 is our strongest bone, in that it is highly elongated (0.7 degrees or 45 pc, with an aspect ratio of 140:1) and \textit{exactly} along a previously-claimed spiral arm trace in p-p-v space, although its orientation makes it less elongated than Nessie on the sky. In figure \ref{fig:Candid5_pos_vel} we show a p-v diagram in the longitude range of BC\_18.88-0.09 and overlay the \citet{Dame_2011} global log-fit to CO for the Scutum-Centaurus arm. We see that the HOPS, BGPS, and GRS-determined velocities associated with filament 5 are highly correlated with this global-log fit, suggesting that BC\_18.88-0.09 is marking a "spine" of the Scutum-Centaurus arm in this longitude range. Moreover, BC\_18.88-0.09 also lies along a CO peak in longitude-latitude space, as evident in figure \ref{fig:Candid5_pos_pos}. By overlaying a trace of the mid-IR extinction feature of filament 5 on a plane of the sky map (integrated in Scutum-Centaurus's velocity range in the region around filament 5) we see that BC\_18.88-0.09 lies in the center of the most intense CO emission. Finally, figure \ref{fig:Candid5_with_tilt} shows that BC\_18.88-0.09 lies within $\approx$ 10 pc of the true physical mid-plane. All these figures taken together indicate that BC\_18.88-0.09 is Nessie's counterpart in the first quadrant, suggesting that Nessie is not a curiosity, but one of several bones that trace significant spiral features. Our study is not the first to look for long filaments associated with spiral structure. \citet{Ragan_2014} and Wang et al. (2015) have undertaken similar studies. However, ours is the first study to specifically look for bones in regions we are most likely to find them, that is, elongated along the galactic plane. Moreover, ours is the only study to create a quantitative set of criteria capable of defining this new class of objects (i.e. galactic "bones").   In the former study, \citet{Ragan_2014} undertook a blind search (not restricted to latitudes where the mid-plane should lie) for long thin filaments (> $1^\circ$) in the first quadrant of the Milky Way, using near and mid-infrared images. In addition to confirming that Nessie lies along the Scutum arm, \citet{Ragan_2014} find seven GMFs of which only one, GMF 20.0-17.9, is said to be associated with Galactic structure (declared a spur of the Scutum-Centaurus arm). Our strongest bone candidate, BC\_18.88-0.09, is a subsection of GMF 20.0-17.9, but, unlike \citet{Ragan_2014}, we argue that BC\_18.88-0.09 runs right down the spine of the Scutum-Centaurus arm in p-v space. We believe the discrepancy arises due to a difference in methodology. \citet{Ragan_2014} group neighboring IRDCs into a single filament, despite a) breaks in the extinction feature b) kinks in velocity structure, occurring at longitudes of $\approx 19.2^{\circ}$ and $18.5^{\circ}$. Since grouping several IRDCs to make a longer structure violates our criteria 5 and 6, we only consider the continuous and kinematically coherent part of the filament (yellow boxed region in figure \ref{fig:Candid5_with_tilt}, longitude=[$18.5^{\circ}$,$19.2^{\circ}$]), which is remarkably parallel to the Scutum-Centaurus arm in p-v space. Likewise, in figure 6 from \citet{Ragan_2014} (analogous to our figure \ref{fig:skeleton}), they represent filaments as straight lines connecting velocities measured at the tips of the filaments while we represent filaments as sets of points whose velocities are determined by the BGPS, HOPS, MALT90, and GRS surveys. Moreoever, \citet{Ragan_2014} only cite the \citet{Vallee_2008} spiral arm fits, despite several updated fits to the Scutum-Centaurus and Norma-4 kpc arms from \citet{Dame_2011} and \citet{Sanna_2014}.   Since \citet{Ragan_2014} find little or no association with their filaments and Galactic structure  Thus, a clear and consistent description of a bone is critical, and, in future studies, we plan to continue to apply the criteria above to achieve consistency. Because we  only know of one long filament in the fourth quadrant and a similar  study as presented here has not yet been performed on the  fourth quadrant, we can only speculate as to why we found no  Nessie-like clouds in the first quadrant despite the similarity in  discovery methods. Are we just not as sensitive to spiral arm filaments  in the first quadrant compared to the fourth? It is possible  that the frequency and orientation of spiral arm filaments and  spurs is different in the two quadrants  Like \citet{Ragan_2014}, Wang et al. (2015) search for large-scale filaments and establish their relationship to Galactic structure after the fact. Rather than searching for filaments elongated along the Galactic plane, Wang et al. (2015) search for the longest, coldest, and densest filaments (aspect ratio >>10) in the Hi-GAL images, within the longitude range of $15^\circ < l < 56^\circ$. Wang et al. (2015) highlight nine filaments as their most prominent, with one of the nine being Nessie. Only one of their filaments (BC\_11.13-0.12, the "snake") overlaps with our sample. Five other Wang et al. (2015) filaments fail one or more of our bone criteria. G24, G26, and G47 lie between 39-62 pc above the physical Galactic midplane (significantly outside our $\pm 20$ pc criteria), while G28 and G65 have aspect ratios of only around 19:1 and 38:1 (less than our 50:1 minimum aspect ratio criteria). G29 and G49 could be potential bone candidates, but without seeing p-v diagrams of the selected filaments (overlaid on log-spiral p-v fits to the Milky Way's arms) it is difficult to determine whether they would satisfy our criterion 4 (within 10 km/s of the global-log spiral fit to any Milky Way arm) and criterion 6 (no abrupt shifts in velocity, of more than 3 km/s per 10 pc, within extinction feature). Though Wang et al. (2014) do find velocity coherence along their filaments, they do say that, in certain clumps, the velocity gradients are much larger, creating the possibility that they might exceed our criterion 5. In future studies, we plan to follow-up on G29 and G49 to determine a) the precise number of bone criteria they satisfy and b) their association with a spiral arm in p-v space. In judging whether a filamentary cloud lies within an arm, or is highly inclined to it, the velocity of the associated gas offers the most relevant evidence. Since Wang et al. (2015) only show the correlation between filaments and spiral structure in X-Y space, we will reanalyze the most promising filaments (G29 and G49) in longitude-velocity space to more accurately determine their correlation with a spiral arm.