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\section{Methodology}  To search for more bones, we visually inspect regions (|$l$|\textless 30$^{\circ}$, |$b$|\textless 1$^{\circ}$) where arms are predicted to lie according to our current understanding of the Milky Way's structure; the expected ($l,b,v$) paths of the Galactic arms are calculated using a log-spiral approximation as described in recent literature \cite{Dame_2011, Vallee_2008}. The predicted positions of the Galactic arms (Scutum-Centaurus, Carina-Sagittarius, Norma-Cygnus, and Perseus) are overlaid on three-color Spitzer GLIMPSE \citep{Benjamin_2003,Churchwell_2009} images in World Wide Telescope (WWT)---a tool that facilitates easy visualization of several layers of data at scales from the full sky down to the highest-resolution details. As part of our initial criteria, we search for long, largely continuous, filamentary mid-infrared extinction features that are near and roughly parallel to the Galactic mid-plane. This initial inspection yielded about fifteen Bone candidates (a video showing how this search worked in WWT is available \href{http://tinyurl.com/morenessies}{on YouTube}, and the original WWT Tour, of which the video shows a capture, is available at the \href{http://dx.doi.org/10.7910/DVN/29934}{Bones of the Milky Way Dataverse}).  For features that appear associated with spiral arms on the 2-D plane of the sky, radial velocity data is needed to establish whether 3-D association with a spiral feature is likely. The filament must have similar line-of-sight velocities along its length to ensure its contiguity. Moreover, the measured radial velocities should be very close to those predicted by the Milky Way's rotation curve for arms at a known distance. To investigate the velocity structure of these fifteen filaments, we employ radial velocity data from five separate radio surveys: HOPS \citep{Purcell_2012,Walsh_2011}, MALT90 \citep{Foster_2011,Jackson_2013}, BGPS spectral line follow-up \cite{Schlingman_2011,Shirley_2013}, \cite{Schlingman_2011,Shirley_2013, Ellsworth_Bowers_2013},  GRS \citep{Jackson_2006} and ThrUMMS \cite{Barnes_2011}. The HOPS, MALT90, and BGPS surveys are all geared towards probing dense regions hosting the early stages of high mass star formation. We utilize $\textrm{NH}_3$ emission from HOPS, $\mathrm{N_2H^{+}}$ from MALT90, and $\textrm{HCO}^{+}$ from BGPS. All three of these thermal emission lines trace dense molecular gas ($\approx10^{4}\textrm{ cm}^{-3}$) and are often found in dense, cool clouds with temperatures less than 100 K \citep{Purcell_2012, Shirley_2013}. As infrared dark clouds tend to harbor cool, high density clumps of gas which fuel the formation of massive stars, all three of these data sets contain spectra for hundreds of regions within the longitude range of the potential Galactic bones. In cases where HOPS, MALT90, and BGPS catalog data are not available along the extinction feature, we also extract spectra from GRS (high resolution $^{13}$CO (1-0) data) and MALT90 \textit{p-p-v} cubes using the spectrum extracter tool in \href{http://www.glueviz.org/en/stable/index.html}{Glue}. Glue is a visualization tool that facilitates the linking of various data sets. We link spectral \textit{p-p-v} cubes from the GRS survey with GLIMPSE-Spitzer mid-infrared images and extract velocities along different regions of the extinction feature; a demonstration of the procedure used to extract velocities in Glue is shown in the appendix. In order to ensure that that GRS velocities are consistent across the filament, we also use the slice extraction tool in Glue to obtain velocity as a function of position along a path that traces the entire extinction feature.The results of the slice extraction along the path of one of our strongest bone candidates, filament 5, is shown in figure \ref{fig:filament5_slice}. Since CO traces lower density gas ($\approx10^2 \textrm{ cm}^{-3}$) and $\mathrm{N_2H+}$, $\textrm{HCO}^+$, and $\textrm{NH}_3$ trace high density gas ($\approx10^4 \textrm{ cm}^{-3}$), the dense gas sources provide much stronger evidence for the velocity of cold, dense, filamentary IRDCs. However, where dense gas sources are not available, the complete and unbiased high resolution GRS survey, although less desirable, allows us to roughly gauge the velocity along entire lengths of filaments. In filaments composed entirely of GRS spectra, we also take HOPS spectra over the entire filament using Glue and confirm that this HOPS-determined velocity agreed with GRS-determined average velocity to within 5 km/s.