ON MOLLUSCA OF THE WEST COAST OF NORTH AMERICA. 365 



It is probable that these lists will hereafter be greatly extended. The 

 shells will be moved from one head to another, according to opinion and 

 opportunities of judgment. Unfortunately, although the West Indian shells 

 were among the first examined, they are to this day very little better known 

 than by the Lamarckian conchologists. Most of the shells in collections are 

 dead and worn, and the dredge has been but little used, especially in the 

 great and doubtless prolific Gulf of Mexico*. At present our best sources 

 of information are — (1.) The Sagra collection from Cuba (mostly poor 

 shells), kept distinct in the British Museum. (2.) The St. Vincent collec- 

 tions of the late Rev. L. Guilding, scattered in the general collections of 

 the British Museum. (3.) The very fine Barbadoes collections of Dr. 

 Cutting in the Bristol Museum. (4.) Prof. Adams' sea-shells from Ja- 

 maica, which have not yet been fully tabulated, though several are de- 

 scribed in the ' Contributions to Conchology.' Others also appear scattered 

 in the ' Zeitschrift fur Malacozoologie,' and other works. The Pacific shells 

 having been so little known to the earlier writters, when there are analogous 

 species, it is fair to suppose that the West Indian forms are intended. This 

 is another reason for their careful study. 



85. But the analogies of the Mazatlan shells extend further than the 

 Caribbean waters. Not merely some West Indian species, as Nitidella cri- 

 braria, found also in the Pacific, have made their way to the east shores of 

 the Atlantic ; but several Mazatlan forms, not yet quoted from the West 

 Indian islands, unexpectedly reappear on the Senegambian and Guinea coast, 

 as though they loved western shores. 



Species ? common to the West {Pacific) American shores and Africa, 

 W. A. = West Africa. S. A. = South Africa. E. ^. = East Africa {Capt. Owen, B.M.). 



West America. Africa. 



1. Saxicava arctica arctica, S.A. 



2. Kellia suborbicularis suborbicularis, W. A. 



3. Isognomon Chemnitzianum Chemnitzianum, W. A. 



4. Lithophagus aristatus caudigerus, W. A. 



5. Ostrea iridescens spathulata, W. A.f 



6. conchaphila conchaphila, W. A. 



7. Placunanomia pernoides pernoides, W. A. 



8. Crepidula unguiformis Goreensis, W. A. 



9. aculeata aculeata, S. A. 



10. Hipponyx antiquatus .. , antiquatus, W. A. 



1 1 . Bankivia varians J varians, S. A. 



12. Natica maroccana (Pritchardi) maroccana, W. A.§ 



13. Marginella cserulescens prunum, W. A. 



14. Nitidella guttata cribraria, W. A. 



15. Purpura pansa patula, W. A. 



* If the " Central American difficulty " should ever draw our Transatlantic brethren, 

 Messrs. Rich, Jewett and Green, to the Caribbsean seas, it is hoped that they will explore 

 them well ; an occupation surely more worthy of a philosopher than killing his brothers ; and 

 a " difficulty " requiring solution quite as much as the ownership of the Mosquito territory. 



f It is believed that Petricola robusta was found in the African oysters ; but this only 

 rests on circumstantial evidence: v. B.M. Mazatlan Cat. p. 19. 



% The solitary young specimen of this characteristic species in the Reigen collection, was 

 taken from the debris of a Spondylus, which is a sea (not shore) shell. 



§ Having very carefully compared large numbers of the West American shells {Pritchardi, 

 Forbes) with a fine series from Gambia, sent by Chief Justice Rankin to the Bristol Museum, 

 I cannot but regard them as identical, both as to shell, operculum, and similarity of variations. 

 The shells called unifasciata may or may not belong to this species : several unquestionably do. 



