548 Coquimbo. part n. 



British T. tetraedra, by the surface having the ribs sharp and well 

 defined to the beak, whilst in the British species they become obsolete 

 and smoothed down ; but this difference is not constant. Prof. Forbes 

 adds, that, possibly, internal characters may exist, which would 

 distinguish the American species from its European allies. 



Spirifer linguiferoides, E. Forbes, PI. V. figs. 17, 18. 



Professor Forbes states (see Appendix) that this species is very 

 near to S. linguifera of Phillips (a carboniferous limestone fossil), 

 but probably distinct. M. d'Orbigny considers it as perhaps in- 

 dicating the Jurassic period. 



Ammonites, imperfect impression of. 



M. Domeyko has sent to Trance a collection of 

 fossils, which, I presume, from the description given, 

 must have come from the neighbourhood of Arqueros ; 

 they consist of — 



Pecten Dufreynoyi, d'Orbig. ' Voyage, Part. Pal.' 

 Ostrea hemispherica, do. do. 



Turritella Andii, do. do. (Pleurotomaria Humboldtii 

 of Yon Buch). 



Hippurites Chilensis, do. do. 



The specimens of this Hippurite, as well as those I collected in my 

 descent from Arqueros, are very imperfect ; but in M. d'Orbigny's 

 opinion they resemble, as does the Turritella Andii, cretaceous 

 (upper greensand) forms. 



Nautilus Domevkus, d'Orbio*. do. do. 



Terebratula senigma, do. do. 



Terebratula ignaciana, do. do. 



This latter species was found by M. Domeyko in the same block of 

 limestone with the T. agnigma. According to M . d'Orbigny, it comes 

 near to T. ornithocephala from the Lias. A series of this species 

 collected at Guasco, has been examined by Professor E. Forbes, and he 

 states that it is difficult to distinguish between some of the specimens 

 andthe T. hastata from the mountain limestone : and that it is equally 

 difficult to draw a line between them and someMarlstoneTerebratulaa. 

 Without a knowledge of the internal structure, it is impossible at 

 present to decide on their identity with analogous European forms. 



The remarks given on the several foregoing shells, 

 show that, in M. d'Orbigny's opinion, the Pecten, 



