1915] 



Clark: Fauna of the San Pablo Group 



493 



This species was listed by the writer in his paper on the Neocene 

 of Kirker Pass as C. richthofeni Gabb, but better specimens show that 

 it should be classed as a new species; it differs from C. richthofeni in 

 having a longer and more slender canal ; the body whorl is less tumid 

 toward the base ; the inner lip is not incrusted as on C. richthofeni; 

 the columella of the latter lacks the oblique groove seen on C. 

 kirkensis. 



Dimensions. — Height about 10 mm. ; greatest width of body whorl, 

 4 mm. 



Occurrence. — In the Lower San Pablo Group near Kirker Pass, 

 University of California localities 1891 ami 102. 



NASSA PABLOBNSIS, n. sp. 

 Plate 65, figures 8 and 9 



Shell fairly heavy, medium in size, slender. Number of whorls to 

 spire seven. Sutures deeply depressed; whorls moderately convex. 

 Surface sculptured by sixteen to eighteen medium coarse longitudinal 

 ribs, with interspaces about equal to the width of the ribs. Surface 

 also covered by revolving ribs which are about as heavy and have 

 about the same width of interspaces as the longitudinal ribbing ; on 

 the body whorl there are nine revolving ribs ; on the whorls of the 

 spire there are four to five ; on the type specimen the junction of these 

 two sets of ribbing gives a nodose effect similar to that seen on N. 

 calif ornica Conrad, a Recent species on the Pacific Coast ; on other 

 specimens this character is not so prominent. On the outer lip there 

 is a fairly prominent ropedike varix ; the back part of the type speci- 

 men is not exposed but on other specimens a second varix is seen on 

 the posterior part of the body whorl, and a faint varix may also be 

 seen on the first whorl of the spire. Inner lip incrusted; columella 

 with four fairly prominent plications or ridges, a continuation of 

 the revolving ribbing of the body whorl. Canal short and reflexed, 

 separated posteriorly from the body whorl by a fairly deep sinus. 



This species is very similar in outline to N. menclica Gould, a Recent 

 species on this coast. It differs in that the longitudinal ribs are closer 

 together and more numerous, and in the presence of the ropedike 

 varices. 



N. pabloensis differs from N. calif ornica in the presence of the 

 varices ; the shell is more slender ; the concentric and longitudinal ribs 

 are closer together and differ in mimber. 



