168 AMERICAN JOURNAL 



at Los Todos Santos Bay, where numbers of specimens were col- 

 lected by Mr. Hemphill. Fossil specimens of the latter have 

 been collected from the post-pliocene formation at Santa Barbara 

 Island, Cal. {vide Geol. Survey of Cal., Paleon. Vol. IT, p. 75). 



The geographical range of the North American species of this 

 genus, which has no representative upon the Atlantic coast of 

 the continent, is as follows: Commencing at the north, we find 

 31. engonatum, Com-., with its northern limit at Baulines (or 

 Bolinas) Bay, which is about twelve miles north of the entrance 

 to the Bay of San Francisco, where I have collected great num- 

 bers of specimens, generally of small size, upon the shales, be- 

 tween ordinary tide-marks ; it extends southerly to San Diego, 

 a range of nearly four hundred miles, where it is represented 

 by a local varietal form, which is the 31. spiratum of Blainville. 

 31. engonatum is by far the most common of the northern spe- 

 cies ; in one instance I collected not less than two thousand spe- 

 cimens, and I find it quite generally distributed along the coast. 

 The finest specimens, averaging twice the size of the Baulines 

 shells, may be found at Lobitas, Point Alio Nuevo, thence to 

 Monterey and some distance southward. In the post-pliocene at 

 San Pedro, Cal., it is found fossil, (Geol. Survey of Cal., Paleon. 

 Vol. II, 75.) It is the 31. unicarinatum, Sby. (vide Conch. 

 Illustr. genus Monoc, fig. 5,). Sowerby's name would apply 

 very well to the var. spiratum, but his figure distinctly repre- 

 sents the general form. 



31. lapilloides, another of Mr. Conrad's species, a handsome 

 and more globose shell than 31. engonatum, is much less abun- 

 dant and far more restricted in range; it equals 31. " puneta- 

 tum, Gray -f brevidens. Conr." (vide Cpr. Supp. Rep. 1863), 

 and M. punctulatum, Gray, vide Sby.'s Conch. Illustr. genus 

 Monoc, fig. 8, where it is well figured. It has not, to my 

 knowledge, been collected north of Monterey, which place, if 

 numbers of individuals are to be considered, seems to be its spe- 

 cific centre. Cooper, in his Geog. Cat. credits it to Catalina 

 Island, which is perhaps its southern limit, but neither of the 

 collections made by Hepburn, Newcomb, Hemphill or Harford, 

 contained a single specimen either from Santa Barbara or San 

 Diego. All of the collections above referred to were examined 

 and noted by me, as well as a collection made at Catalina Island 

 by Mr. Cummings, of San Francisco, which contained many 

 rarities, but not a specimen of this species. I therefore infer 

 that, though reported from Catalina Island, it is seldom met with 

 even there. This conclusion is further confirmed by the absence 

 of the species from several parcels of shells from said island 

 received by me at various times from my friend W. M. Cubery,. 

 Esq. 



