110 THE NAUTILUS. 



may be sexual, but, if not, it seems that it is specifically distinct. 

 The shell is small, in the adult stage averaging about 62 mm. in 

 length, against 90 to 110 mm. for the fully adult cnrpenteriana. It 

 is proportionately much heavier, the anal fasciole is more strongly 

 constricted, and the appressed margin of the whorl does not approach 

 as closely to the periphery of the preceding whorl as in that species. 

 The periphery is often marked by a minutely beaded or undulate 

 thread, and is more nearly midway between the sutures on the spire 

 than in carp enter iana. The aperture is shorter than the spire in 

 nearly every case, while the reverse is true of carpenteriana. The 

 average proportions of the new form, which I propose to call B. 

 tremperiana, and of B. carpenteriana, from measurements of 8 and 

 25 specimens respectively, are as follows : 



B. tremperiana: aperture 32.1, spire 32.2, diam. 20.7 mm. 



B. carpenteriana : aperture 34.6, spire 29.4, diam. 22.6 mm. 



B. stearnsiana : aperture 26.2, spire 23.2, diam. 17.8 mm. 



Dr. Tremper writes me that his examination of his series of 33 

 specimens of tremperiana confirms the above distinctions. 



B. tryoniana Gabb seems (after an examination of nearly all the 

 extant specimens) to be merely a variety of carpenteriana, with an 

 unusual development of tubercles or nodes on the periphery or 

 shoulder of the whorls. 



The range of B. carpenteriana extends from Tomales Bay, north 

 of San Francisco, to San Diego, in 20 to 158 fathoms, and to Cerros 

 Island. B. tremperiana is known from off Santa Cruz, California, 

 south to Cerros Island, and has been dredged living in from 29 to 

 822 fathoms by the U. S. S. Albatross, a remarkable bathymetric 

 range. 



MODIOLUS DIEGENSIS, new species. 



In Mr. Gripp's collection, which is notable for the taste and care 

 with which the specimens are displayed, I found a small species of 

 Modiolus or Myrina from San Diego, which seems to be undescribed. 



Shell small, zoned with dark blue, the unbones usually white, 

 covered wz'th an olivaceous brown periostracum; anterior end very 

 short, rounded, with two or three radial grooves externally; unbones 

 moderately prominent; dorsal profile ascending, nearly straight, 

 subangulate behind, the margin carried with a broad sweep to the 

 base where it meets the posterior end of an obscure ridge radiating 



