260 TRIONYCHID®. 
Gymnopus spiniferus, part., Dum. § Bibr. ii. p. 477, pl. xxii. fig. 1 
(1835). 
Tee pee Dekay, N. ¥. Faun. iii. p. 6, pl. vi. fig. 11 (1842). 
Tyrse argus, Gray, Cat. Tort. p. 48 (1844), and Knowsley Menag. 
pl. — (1846). 
Trionyx a Gray, Cat. Sh. Rept. i. p. 68 (1855). 
Aspidonectes spinifer, Agassiz, Contr, N. H. U. S.i. p. 403, pl. vi. 
fies. 1 & 2 (1857). 
Gymnopus olivaceus, Wied, N. Act. Ac. Leop.- Carol, xxxii.i. p. 55, 
pl. v. (1865). 
Callinia spinifera, Gray, Proc. Zool. Soc. 1869, p. 222, and Suppl. Cat. 
Sh. Rept. i. p. 109 (1870), and Proc. Zool. Soc. 1873, p. 60, figs. 
Very closely allied to the preceding, but carapace flatter *, snout 
and interorbital region narrower, and markings different. Dorsal 
disk with small black spots and ring-like markings, which may 
become indistinct with age; young with a pale, black-edged border 
to the dorsal disk; a light, black-edged streak on each side of the 
head, passing through the eye, uniting with its fellow at the base 
of the proboscis ; limbs spotted and marbled with black. 
Length of dorsal disk 30 centim. 
Middle and Northern tributaries of the Mississippi; Ohio; Saint 
Lawrence River. 
a. Her., spir. Foxbury, Pensylvania. Smithsonian Institution. 
6. Hgr., spir., skull Wabash River. 
separate. 
c,d, e. Her. & yg. N. America. 
spir. 
J. Her., stftd. —-?P Lord Derby[P.]. (Type 
of T. argus.) 
15, Trionyx muticus 7. 
Trionyx muticus, Lesueur, Mém. Mus. xv. p. 263, pl. vil. (1827) ; 
Leconte, Ann. Lyc. N. ¥. iii. p. 95 (1850) ; Holbr. N. Am. Herp. 
ii. p. 19, pl. ii, (1842); Gray, Cat. Tort. p. 50 (1844), and Sh. 
Rept. i. p. 69 (1855) ; Strauch, Chelon. Stud, p. 174 (1862), and 
Verth. Schildkr. p. 125 (1865). 
Gymunopus muticus, Dum. § Bibr. ii. p. 482 (1855). 
Amyda mutica, Agassiz, Contr. N. H. U. S.i.p. 399, pl. vi. figs. 6 & 
7 (1857); Gray, Suppl. Cat. Sh. Rept. i. p. 95 (1870); Baur, 
Zool. Anz. 1887, p. 99. 
Potamochelys ? microcephala, Gray, Proc. Zool. Soc. 1864, p. 87. 
Callinia microcephala, Gray, Proc. Zool. Soc. 1869, p. 222, and Suppl. 
Cat. Sh. Rept. i. p. 108, and Proc. Zool. Soc, 1873, p. 62, figs. 
Differs from the preceding in the much narrower, sharply pointed 
snout, the absence of conical tubercles on the anterior border of the 
dorsal disk and on the posterior cartilaginous margin, and in the 
absence of a papilla on each side of the nasal septum, which is 
considerably wider than in other Trionychoids. Entoplastron, in the 
* A small eighth pair of costal plates is present in one of our specimens. 
+ In addition to the single specimen in the Museum, I have recently examined 
® fully adult living specimen, from which the following notes are taken. 
