58 MAZATLAN BIVALVES 



85, Teigona aegentina, Scnv. 



Cytlierea argentina, Proc. Zool. Soc. 1835, p. 46. — Sanl. Descr. 

 Cat. p. IQ^:— Wood's Suppl. pi. 15, f. lo— Phil. AhbiU. 

 Conch. Cyth. pi. 3, f. 5.— Sow. TJies. Conch, p. 622, pi 129, 

 f. Q2.—?Menl'e Zeitsch.f. Mai. 1847, p. 189, no. 55. 



Trigona argentina, Desh. JB. M. Cat. Ven. p. 50. no. 16. 



This shell may be kno'vm at once from those varieties of 

 T. radiata which most approach it by the very remarkable and 

 constant shape ; being most regularly excurved along the ven- 

 tral ]nargin, incurved on the anterior and straight on the pos- 

 terior dorsal lines. Coloiu* didl white, with light olive green 

 epidermis ; often with two rays of violet within. The anterior 

 cardinal tooth is much larger than in T. radiata, and the pos- 

 terior tooth does not display rugose sulcations. The anterior 

 adductor scar is less deeply impressed and more evenly bounded. 

 Long. 2-12, ktt.2-Q, alt.'l-o2. 



Sab. — Gulf of Nicoyia, in sand banks at low water, Cuming. — 

 ? Guaymas, Zieid. Green, (Gould ms.*). — Mazatlan ; 3fel- 

 chers. — Do. very rare ; Upool Sf Savre Coll. 



Tablet 245 contains 3 miuute valves, the smallest '■04 across, 

 whicli may belong to this species. 



Tablet 246 contains 2 specimens. The smallest displays the 

 violet raj's, and an abnormal lamina within. 



86. Tbigona ?? ceassatelloides, Conr. 



Ann. Nat. Hist. Soc. Philad. t. 7, p. 253, pi. 19, f. 11.— Hinds, 

 Toy. Siilph. Moll p. 65, pi. 21, f. l.—Desh. B. M. Cat. Ven. 

 \). 46, no. 1. 



Cji:herea crassatelloides, Hani. Descr. Cat. p. 106: — Wood 

 Suppl. pi. 15, f. 32.— -Sow. Thcs. Conch, p. 612, pi. 127, f. 1—3. 



Tablet 247 contains 2 small valves, (the smallest '04 across) 

 wliich have the shape aud thickness of this species. Their 

 identity however is doubtful, T. crassatelloides belonging 

 strictly to the Californian faima, where it attains a diameter 

 of 5 inches. (Woodw. Nutt.) 



* Dr. Gould writes "Venus straminea, Conr. = argentina ? " Tapes straminea, 

 Conr. is the Californian representative of T. Listrionica or T. grata. It is pro- 

 bable therefore that our shell is meant, as Tr. argentina is a well known and 

 constant form. It is possible however that it may not be known to Gould, and 

 that the first shell is meant : also that JVIenke's Cvtherea argentina is one form 

 of T. radiata. 



