Art. 11 NEW AMERICAN MARINE MOLLUSKS BABTSCH 31 



render the axial ribs obscurely nodulose at their junction. The 

 spaces separating the spiral cords are a little less wide than the cords. 

 Periphery of the last whorl marked by a sulcus, which is crossed by 

 the continuation of the axial ribs, which extend partly over the base, 

 but evanesce soon after passing the periphery. Base short, strongly 

 rounded, marked by nine equal and equally spaced prominent spiral 

 cords, which are a little wider than the spaces that separate them. 

 Aperture subcircular ; posterior angle obtuse ; outer lip reinforced by 

 a callus at the edge; inner lip curved and appressed to the base; 

 parietal wall covered by a moderately thick callus. 



The type. Cat. No. 340938, U.S.N.M., was collected by Mrs. Old- 

 royd at Burrard Inlet, British Columbia. It has four whorls re- 

 maining and measures, length, 2.2 mm.; diameter, 2 mm. Cat. No. 

 363778, U.S.N.M., contains two specimens from the same gathering. 

 Five additional specimens from the same station are in the Oldroyd 

 collection. 



This species is nearest related to Alvania 7'oscma from off Santa 

 Rosa Island. It differs from this by its less acute outline, by having 

 the whorls more rounded, and also in other details of sculpture. 



? RISSOELLA CALIFORNICA, new species 



Plate 4, fig. 2 



Shell small, thin, semitranslucent, bluish white, broadly ovate. 

 Nuclear whorls smooth, scarcely differentiated from the postnuclear 

 turns. Postnuclear whorls very strongly inflated, strongly rounded, 

 marked by rather strong, retractively slanting, incremental lines and 

 very feebly developed, almost obsolete spiral threads. Periphery of 

 the last whorl inflated, strongly rounded. Base short, inflated, 

 strongly rounded, with a rather broad, open umbilicus which is 

 marked at its external termination by an obsolete angle. The 

 sculpture of the base is like that of the spire. Aperture broadly oval, 

 rather expanded at the junction of the basal and outer lips. Posterior 

 angle acute; outer lip thin; inner lip strongly curved and expanded 

 over the parietal wall, thus rendering the peritreme complete; the 

 outside of the inner lip at the umbilicus is marked by strong incre- 

 mental lines. 



The type. Cat. No. 362453, U.S.N.M., was collected by Dr. R. H. 

 Tremper on rocks at San Clemente Island, California. It has 4.2 

 whorls and measures, length 2.4 mm. ; diameter, 1.16 mm. 



I am placing this species in the genus Rissoella with some doubt, 

 but until I will have seen anatomic material I hesitate to give it a 

 distinct generic designation. 



A topotype of this species is in Doctor Tremper's collection. 



