42 mazatlan bivalves 



Family DONACID^. 



Gentts IPHIGENIA, Schum. 

 Si/ii. Capsa, Lam. 1818, (non 1801.) Donacina, Fer. 



69. Iphigenia altiob, Sow. 



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



Man. Si/n. Test. Viv. p. '235.— Hani. Bescr. Cat. p. 86 — 



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



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



Shell very variable in 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.V, tat. 1"B7, alt. "56. 



Longest „ „ „ 1'88, „ 2'54, „ I'll. 



Aberrant „ „ „ 1-72, „ 2 •12, „ l^OS. 



JTrti.— Gulf of Nicoyia, in coarse gi-avel, 12 fm. Cuming. — Var. 

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

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

 ^L'pool Sf Havre Coll. — The Atlantic analogue is I. Brazili- 

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

 Justice JRankin, Bi'istol 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 ? l3:vigata, ? cujus. 



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

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

 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 undeseribed species. I have seen it with the 

 name Capsa L-vvigata. b\it do not know on what authority. It 

 is characterized by very overlapping imibos ; subcarinated, 

 Bubtruncated posterior side ; deep posterior ventral sinus ; 



