92 



gulum anticLim armatis : intus alba, dentibus marginalibus luteo 

 tinctis. Long. 3^ ; alt. 3 ; lat. 2^ poll. Inhabits San Diego. 

 Lieut. Green. 



This resembles C. pseudolima, and has been regarded as such ; 

 but the position of the spines at one angle of the ribs instead of 

 along the middle, and the color of the marginal lip, which in 

 that shell is roseate, may alone distinguish them. It has also a 

 more rounded outline and more globular form, and the ribs are 

 more numerous ; the grooves between the ribs are deeper. 



Anodon cicoNiA. T. solidula, transversa, oblongo-ovata, ven- 

 tricosa, epidermide lutescente-corneo induta ; apicibus ad trien- 

 tem anticum longitudinis positis ; latere antico angusto, rotun- 

 dato ; latere postico dilatato, ad apicem acuto ; margine dorsali 

 haud angulato ; margine ventrali rectiusculo, antice hiante ; de- 

 clivitate postico tumido, haud angulato ; margarita ex ochraceo 

 incarnata, demum argentea : cavositas apicalis ampla. Long. 4 ; 

 alt. 2| ; lat. 1^ poll. Mexico ? Lieut. Green, Maj. Rich. 



It is evidently a tropical type, and resembles A. anserina, 

 from Brazil ; it is thicker in substance, more tumid on the pos- 

 terior half, and the epidermis and nacre are quite differently 

 colored. The posterior dorsal and ventral margins have a cor- 

 responding slope and meet at the middle of the altitude. It is 

 more like A. implicata than any other North American species. 



LiTHODOMus FALCATUS. T. fragilis, sub-cylindracea, falcata, 

 postice ad declivitatem umbonalem valde angulata, margaritacea 

 epidermide crasso castaneo rugis interdum bifurcatis corrugato 

 induta, apicibus ad octantem anteriorem positis, valde involutis<5 

 latere antico dilatato, subgloboso ; latere postico arcuato, coarc- 

 tato-acuminato, superne fimbriato. Long. 3 ; alt. et lat. ^ poll. 

 Monterey, in indurated marly clay. 3Iaj. Rich. 



The slender, falcate, and angular form of this shell clearly dis- 

 tinguishes it from all other species. 



Mytilus glomeratus. T. parva, solidula, arcuatim oblongo- 

 ovata, postice obtusa, nitida, ex indico nigrescens ; apicibus re- 

 motis, excurvatis ; valvis ventricosis, oblique subangulatis ; mar- 

 gine ligamentali recto demum subito arcuato; margine ventrali 

 recto vel excurvato ; cardinis altera valva dentibus duobus, 



