42 MAZATLAN BIVALVES 



FAMILY DONACID^E. 



GENUS IPHIGENIA, Schum. 

 Syn. Capsa, Lam. 1818, (non 1801.) Donacina, Fer. 



4 69. IPHIGENIA ALTIOK, Sow. 



Capsa altior, Proc. Zool. Soc. 1832, p. 196, (teste C. B. Ad.) 



Mull. Syn. Test. Viv. p. 225. Hani. Descr. Cat. p. 86. 



Hani, in Suppl. to Wood's Ind. Test. pi. 14, f. 34. C. B. 



Ad. Pan. Shells., p. 276, no. 453. 



Shell very variable iu outline, sometimes nearly equilateral, 

 sometimes much produced anteriorly, sometimes incurved at 

 the posterior ventral margin. The outside has the usual 

 olivaceous epidermis. The inside is more or less stained with 

 violet. Bifidity of cardinal teeth more or less developed : 

 lateral teeth almost evanescent in one valve, absent in the other. 



Smallest specimen measures long. 1', lat. 1*37, alt. '56. 



Longest 1'88, 2'54, I'll. 



Aberrant 1'72, 2'12, 1'03. 



Hob. Gulf of Nicoyia, in coarse gravel, 12 fm. Cuming. Var. 



Tumbez, thin mud, 5 fm. Cuming. St. Elena, Jay. Panama, 



extremely rare, C. B. Adams. Mazatlan : very common ; 



L'pool fy Havre Coll. The Atlantic analogue is I. Brazili- 



ensis. A closely allied species is from the Gambia ; Chief 



Justice Ranlcin, Bristol Mus. 



Tablet 132 contains 5 specimens in the normal state. 133, 



5 specimens more transverse. 134, 5 specimens indented. 

 135, 2 specimens of abnormal growth. 136, 1 specimen with 

 very thin epidermis. 



70. IPHIGENIA PLJEVIGATA, ?cujus. 



This shell is regarded by Dr. Gray as an abnormal variety 

 of I. altior. It has much more the shape of I. Braziliensis. 

 The most deeply indented I. altior is far removed from it. 

 Mr. Cuming has similiar specimens from the same coast, which 

 he regards as an undescribed species. I have seen it with the 

 name Capsa Isevigata, but do not know on what authority. It 

 is characterized by very overlapping umbos ; subcarinated, 

 sub truncated posterior side; deep posterior ventral sinus; 



