366 report— 1856. 



The following species might be divided into groups answering to B, C, and 

 D of the West Indian parallels. 



1. Discina Cumingii striata, W. A. 



2. Pholadidea melanura clausa, W. A. 



3. Parapholas acuminata branchiata, W. A. 



4. Tellina rufescens perna, Spl. (Madagascar.) 



5. Iphigenia laevigata sp., W. A. (Bristol Mus.) 



6. Trigona, var. Hindsii tripla, W. A. 



7. planulata ? bicolor, W. A. 



8. Diplodonta semiaspera circularis, W. A. 



9. Pectunculus nmlticostatus inaequalis (Krauss not Reeve), S. A. 



10. Area grandis senilis, W. A. 



11. Gadinia pentigoniostoma afra, W. and S. A. 



12. Crepidula onyx * hepatica, Krauss. 



13. Cerithium maculosum adustum (? Red Sea). 



14. stercus-muscarum ocellatum, E. A. 



15. Terebra armillata interstincta, W. A. 



16. Euryta fulgurans sp., E. A. 



17- aciculata ? Cosentini. (Mediterranean, &c.) 



18. Aragonia testacea hiatula + Steeriae, W. A. 



19. Harpa crenata rosea, W. A. 



20. Vitularia salebrosa vitulina, W. A. 



21. Purpura biserialis haemastoma, W. A. 



The comparative preponderance of bivalves in these lists is still apparent. 



86. The Kellia suborbicularis, Lasea rubra, Saxicava arctica, and Hydro- 

 bia ulvce, of the Gulf, even belong to the British fauna. The DioneChioncea is 

 so like the D. Chione of our southern shores, that Mr. Sowerby at first united 

 them, quoting under Cyiherea Chione, "Mr. Cuming's specimens are from 

 Mazatlan," while the dull S. Pacific specimens were described as C.squalida, 

 and the banded ones of the same species (by Dr. Gray) as C. biradiata. 

 The CcBCum glabrum of the British, and C. glabriforme of the Mazatlan seas 

 are almost indistinguishable. The same may be said of the form Leiostraca 

 distorta. The Cerithiopsis tubercularis and C. tuberculides are most closely 

 allied ; as are also Byssoarca mutabilis and tetragona, B. solida and lactea, 

 Tellina donacina and donacilla, Modiola modiolus and capax, Thracia 

 squamosa and villosiuscula, Acmcea mesoleuca and testudinalis, Galerus 

 mammillaris and Sinensis, Ianthina striulata and communis, I. prolongata 

 and pallida, Jejfreysia bifasciata and opalina, and Nassa crebristriata 

 and reticulata. The Gouldia varians may compare with Astarte triangu- 

 laris and Tornatina infrequens with Cylichna mammillata. The reappear- 

 ance of the rare genera J/ontacuta, Lepton, and Barleia, is also worthy of 

 notice. 



87. Besides these analogies with the Atlantic shells, there are a few 

 singular exceptions to the general dissimilarity with the Asiatic and Indo- 

 Pacific faunas. Thus we have the Japanese Cytherea petichialis reappearing 

 at Mazatlan ; and Nassa acuta most closely resembling an Australian species 

 in Mr. Cuming's collection. The Oliva Duclosi is quoted from the Pacific 

 islands ; as are also the ubiquitous Natica maroccana and Nitidella cribraria, 

 the pelagic Ianthina striulata, the sedentary Hipponices barbatus and 

 Grayanus ; and a few other species, concerning which there is a fair chance 

 of inaccuracy, especially in shells from " Lord Hood's Island." 



88. Of the land and freshwater shells little is yet known except those 

 brought from Oregon. These are of a different type from those of the 



* Dr. Dunker also quotes Cr. Peruviana = dilatata from the Guinea coast. His solitary 

 specimen may be from ballast ; but it has been plentifully received as from Mauritius. 



