40 Crs'OSTERNID.^. 



a. $,si>ir, ■Wa'sliiiifrton, Smitbsonian lustit. 



b-c Y",'., spir. Floridii. I'l Doiibleday, Esq. [P.]. 



rf. Yg., skel. Florida. E. Doubleday, Esq. [P.]. 



e-h. r? , 2 , it li^., spir. New Orleans. E. Doubleday, Esq. [P.J. 



i-k. Yjr., spir. New Orleans. (Types of C. hippocrcpis.) 



I, in, n. cf 2 1 stffd. Louisiana. 



o,p. S, stfTd. N. America. (Types of C. ohlon(]um.) 



q. Il^jrr., sbell. N. America. (Type of C. doubMayii.) 



r. Y<r., spir., very bad .state. N. America. {Tyy)e oi C. punctatum.) 



g. 2 , stlfd. N. America. E. "Doubleday, Esq. [P.]. 



t, u. Yg., .spir. N. America. Sir E. Belcher [P.]. 



r, w. 2 .t 11.1^., sbells. N. America. 



X. 9 , spir. ? (T^-pe of Sivanka fasciata.') 



V. 9.skel. ? 



'z ?. Ilgr., stflfd. ? 



The latter specimen, referred with some doubt to this species, is 

 specimen c of Gray's G. Jilppocrepis. As already noticed by Gray, 

 it is anomalous in havin? the pectoral and abdominal shields united ; 

 it differs also from all C'inoxterna in havinj^ only '21 shields round 

 the marjrin of the disk, instead of 23. The carapace is much more 

 depressed than in C. hijypocrepis, of which it is, however, perhaps 

 only an anomalous specimen. 



Cinosternnm sonoriense, Lecoute, Proc. Ac. Philad. 1854, p. 184 

 (TJii/rosternum sonoriense, Agassiz, Coutr. i. p. 428, pi. v. figs. 8-11), 

 appears to be very closely alUed to the preceding species. The dif- 

 ferential characters have not been clearly defined. — Hah. Arizona. 



5. Cinostermim flavescens *. 



Platythyra flavescens, Ayassiz, Contr. N. II. U. S. i. p. 430, pi. v. 



figs. 12-1.5 (1857). 

 Cinosternum flavescens, Cope, Check-List N. Am. Bept. p. 52 



(1875) ; Coues, in Whevler's E.vplor. Surv. W. 100th Mer. v. 



pi. xvii. (1875). 



Jaws weak, beak not hooked. Nose short. Suture between the 

 pectorals nearly as long as that between thehumerals (in the adult). 

 Otherwise apparently like C. pensi/Jvanicum, but stouter. Yellowish 

 green, shields edged with black ; beak unspotted. 



Length of shell 11 ccntim. 



Arkansas, Western Texas, and Gila River. 



6. Cinosternum henrici. 



Cinosternum henrici, Leconte, Proc. Ac. Philad. 1850, p. 4 ; Yarrow 

 in Jf 'heeler's Hep. Rrplor. Surv. W. 100th Mer. v. p. 583, pi xvi' 

 (1875). 



Swanka henrici, Gray, Suppl. Cat. Sh. Pept. i. p. G9 (1870). 



* This species has never been described, and rests on the generic descripUon 

 publislied by Agassiz, in which nothing but cranial characters are given, and 

 on the two Cgui-es (quoted, Agassiz's being that of a quite young specimen. ' 



