214 



Long. 3 ; alt. et lat. £ poll. Monterey, in indurated marly clay. 

 Maj. Rich. 



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

 guishes it from all other species. [A specimen in the cabinet of Mr. 

 Cuming, considered as coming from New Zealand, has been described 

 by Philippi under the name of Litliophagus Gruneri. The resem- 

 blance to our shell is very great if not identical. An error as to the 

 locality may have been made.] 



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

 ovata, postice obtusa, nitida, ex indico nigrescens ; apicibus remotis, 

 excurvatis ; valvis ventricosis, oblique subangulatis ; margine liga- 

 mentali recto demum subito arcuato ; margine ventrali recto vel 

 excurvato ; cardinis altera valva dentibus duobus, altera tribus ; intus 

 argentata, ad limbum nigra ; cicatricibus profundis. 



Long. -§ ; alt. f poll. San Francisco. Maj. Rich. 



A very curious species, clustering on sea-weed in the most crowded 

 manuer, so that two adjacent specimens sometimes wear each other 

 nearly through, from friction in opening and shutting. This circum- 

 stance, with the strong hinge and deep cicatrices, show that the speci- 

 mens are mature. The byssus is coarse, wax yellow. 



Lima tetrica. T. solida, oblique ovato-triangularis, albida, costis 

 radiantibus ad 18 squamis semi-erectis posticis longioribus armatis, 

 horrescens ; apicibus acutis, elevatis, remotis, muriculatis ; margineli 

 byssali rectilineari, hiante ; ami cardinali lata, valida ; fovea ligamen- 

 tali minhne profunda, costa transversali suffulta. 



Long. 1^; alt. 1-|-; lat. -| poll. Gulf of California, La Paz. Maj. 

 Rich. 



Compared with L. squamosa, it is narrower and more compressed ; 

 the dorsal and ventral margins are less broadly rounded ; the scales 

 are more crowded, twice as long, indexed at their points, and much 

 more developed at the dorsal margin ; there are no stria? on the 

 dorsal area. The remarkable brace or rib under the ligament pit, by 

 which a deep cavity at the apex is formed, is remarkable, but possibly 

 accidental. 



Avicula sterna. T. solidula, badia radiis pallidis ornata ; 

 epidermide cinerea serratim fimbriate induta ; apicibus ad quad- 

 rantem anteriorem positis ; ala semicirculari, modice obliqua, declivi- 

 tate umbonali tumido, abrupto ; cauda longissima, gracili ; auriculis 

 magiiis, radiatim striatis ; fissura byssali profundissima, acutangulari : 

 margarita argentata, valde iridescens ; limbo fusco-marmorato. 



Long. 21; lat. 1*-; alt. | poll. Inhabits Mazatlan. Lieut. Green. 



Has the general appearance of A. semi-sagitta, but the wing is less 

 oblique and curves directly into the cauda without any sinus; the 



