22 SYSTEMATIC PALEONTOLOGY 



The species velox has not been reported from Maryland. 

 Occurrence. — Calvert Formation. Charles county near the Patux- 

 ent river. 



Collection. — Philadelphia Academy of Natural Sciences. 



Zarhachis tysonii Cope. 



Zarhachis tysonii Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 9. 

 Zarhachin tysonii Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. vii, p. 435 



(mention only). 

 Zarhachis tysonii Cope, 1890, Amer. Nat., vol. xxiv, p. 614. 



Description. — This species was based on one posterior lumbar. " The 

 attenuated form characteristic of the genus is accompanied by broad 

 diapophyses showing that, as in PriscodelpJiinus, the species differ in 

 the number of posterior vertebrae which exhibit the contraction of the 

 diapophyses. 



" The specimen preserved belonged to an adult animal. It was 

 apparently one of the posterior lumbars, as there are two feeble longi- 

 tudinal ridges beneath, whose interval is again obtusely ridge and per- 

 forated by several foramina. The inferior outline is strongly concave 

 in longitudinal section, and all the planes are concave in transverse 

 section. The articular faces are a little wider than deep. The neura- 

 pophyses occui)y a base of .75 the length of the centrum. The diapo- 

 physes are about equidistant between them and the nearest inferior 

 ridge. 



Total length of centrum 48 lines (96 mm.) 



Transverse diameter articular face 29 lines (58 mm.) 



Vertical diameter articular face 27 lines (54 mm.) 



Width neural canal (internal) 5 lines (10 mm.) 



Width between inferior ridges 8 lines (16 mm.)" 



Occurrence. — St. Mary's Formation. JSTear the mouth of the Patux- 

 ent river. 



Collection. — Keported in the Museum of the Philadelphia Academy 

 of Natural Sciences. 



