MAZATLAN BIVALVES 59 



Sah. — Sta. Barbara ; Nuttall, Col. Jewett. — San Diego ; Lieut. 

 G-reen. — Mazatlau ; Lieut. Green. (Gould ms.) — ?? do ; from 

 shell washings ; L'pool Col. 



87. Teigona planulata, Brocl. Sf Soto. 



Cytherea plannlata, Zool. Journ. vol. v. p. 4S.—Sow. Gen. f. 2. — 



Rve. Coneh. Syst. vol. i. p. 94, pi. 69, f. 2.—Eanl. Bescr. Cat. 



p. \Qo.—Zool. Beech. Voy. p. 1-51, pi. 43, f. Q.—Sow. TJies. 



Conch, p. 618, no. 20, pi. 127, f. 13. 

 Vemis planulata, B. M. Cat. B'Orh. Moll. p. 66, no, 587. 

 Trigona planulata, Gray Cat. Cyth. Anal. vol. viii. p. 304. — 



Desh. B. M. Cat. Veri. p. 48, no. 8. 

 + Var. sufFusa, Soio. Proc. Zool. Soc. 1835, p. 46. 

 + Cytherea undulata, Sow. Thes. Conch, p. 618, no. 21, pi. 127, 



f, \2.— (Trigona u.) Desh. B. M. Cat. Ven, p. 48. no. 9. 

 =Donax Lessoni, Desh. Enc. Meth. vers. t. 2. p. 99. 

 = (teste Desh.) Cytherea mactroides, Lam. (non Born nee Sotv.) 



An. s. Vert. vol. vi. p. 307, no. 27. — Deless. Bee. de Coq. pi. 8, 



f. 2.—Eanl. Descr. Cat. p. 99 : Wood Suppl. pi. 13, f. 17. 



The very illustrious Deshayes in his later works seems much 

 more disposed to the multiijlication of species than he was in 

 his earHer edition of Lamarck. He follows Sow. jun. in divid- 

 ing the C. planulata of Brod. Sf Soto. The C. undulata is 

 discriminated by its more equal form, greater solidity, absence 

 of posterior gape, distinctness of lunule and style of painting. 

 I have not found any one of these characters constant. The 

 species varies almost as much as its more swollen congener, 

 T. radiata. In form there is a gradual passage between the 

 two. The undtdata; are if anything thinner than the planulata;. 

 The breaking up of the coloured rays proceeds by insensible 

 gradations, and the colouring of the interior varies greatly. 

 The gaping is either posterior, or anterior, or both, or some- 

 what ventral, or none, just as it happens. The beaks are scarcely 

 ever tipped with purple. The painting of the two valves does 

 not always correspond. The teeth are very smaU and angular ; 

 anterior lateral much prolonged. The W. African analogue is 

 T. bicolor, Hani. 



Typical form measures long. 2', lat.2'Z, alt.V. 



Var. undulata „ „ 1*78, „ 2"2, „ '88. 



Hah. — Panama, Cuming. — Cldli ; Coquimbo ; D'Orbigtiy. — 



Foimd abundantly near Mazatlan ; Lieut. Belcher. — Maz- 



atlan ; not common ; L'pool Col. — Var. suffusa ; Salango, 



sandy mud, 9 fm. Cuming. — Var. undulata, do. Cuming. 



