24 PROCEEDINGS OF TIIE ACADEMY OF 



think the identifications must be reconsidered, and one of the 

 names originally proposed by himself (G. megalocephalus), be 

 retained. The species are thus distinguished: 



I. Inguinal scuta two. 



Shell depressed, broad, carinse very weak ; one long anal plate ; inguinals 

 transverse ; tail smooth ; head brown, shielded above to behind the eyes. 



C. SEVERUS. 



Shell with three elevated keels, the carapace emarginate between the anal 

 scuta ; one short anal plate ; inguinals longitudinal ; tail with four rows 

 of tubercles ; head white spotted above, brown spotted below. 



C. PICTUS. 



II. Inguinal scuta one or wanting. 



Head very wide, smooth above ; two anal scuta ; lobes of plastron sub- 

 similar ; dorsal keel grooved. C. megalocephalus. 



Head narrower, with a horny shield on the top of the nose ; posterior lobe 

 of plastron narrower and more acute than anterior ; dorsal keel simple. 



C. AN GU STATUS. 



CLAUDIUS SEVERUS, Cope, sp. nov. 



Carapace an elongate oval, with convex sides; the upper sur- 

 face nearly plane in profile, rising anteriorly, sloping to the an- 

 terior margin, and descending rather abruptly to the posterior. 

 General form rather depressed, the middle line including the entire 

 width of the vertebral scuta below the level Of the proximal part 

 of the costals. The latter present an obtuse longitudinal carina 

 on the two median. The two central vertebral scuta also possess 

 a weak keel, of which a trace appears anteriorly on the fifth or 

 last; first and second flat. The scutal sutures bounding the ver- 

 tebrals, costals, and marginals (except those between the last) 

 are bounded by flat but marked grooves of the shell. Thus a 

 continuous band-like groove extends round the carapace aboA r e the 

 marginal bones, and is continuous with a similar one passing 

 along the anterior margin of each costal, and undulate grooves 

 along the margins of the vertebrals. The first costal is one-fourth 

 longer than the second. The vertebrals are hexagonal, longer 

 than broad, with a rounded notch behind and projection in front. 

 The first is narrowed urceolate, deeply notched behind, and mar- 

 gining nearly half the first marginal in front. The nuchal is 

 broad transversel}", and very narrow; the anterior one narrower 

 than the posterior. The last and penultimate are a little wider, 



[April 1G, 



