Clark: The San Lorenzo Series of Middle California 



181 



Pseudoperissolax differs from the typical Perissolax, as described 

 by Gabb, 153 in having a higher spire and an entirely different kind 

 of scnlpture. Undoubtedly several different genera bave been in- 

 cluded under the name Perissolax. 



The genus Pseudoperissolax differs from the genus Busy con prin- 

 cipally in the canal, which is more slender, the aperture narrower ; 

 it lacks plication and infolding found on the inner lip of Busy con; 

 also the biangulate character of the body whorl of the genus Pseudo- 

 perissolax distinguishes it from Busycon. 



Genus PSEUDOPERISSOLAX, n. genus 

 PSEUDOPERISSOLAX MERRIAMI, n. sp. 

 Plate 21, figure 4; plate 22, figures 10 arid 15 

 Type specimen 11161, Coll. Invert. Palae. Univ. Calif., loe. 2033 



Shell fusiform ; apex acute ; number of whorls seven or eight ; sutures appar- 

 ently slightly channeled. Body whorl fairly large, biangulate ; only upper angle 

 shows on whorls of spire; each whorl broadly subtabulate posteriorly between 

 angle and suture, the subtabulate area sloping up obliquely to suture; whorls of 

 spire below subtabulate area straight, also straight on body whorl down to anterior 

 angulation, below which surface slopes in very rapidly to canal. Thirteen or 

 fourteen blunt but rather prominent nodes on each angulation of body whorl ; 

 surface also covered by numerous fine, closely crowded, spiral ribs, every other 

 rib being slightly heavier than the one between. Canal straight, fairly long. 



Dimensions. — Height, about 47 mm. ; greatest width of body whorl, about 

 17 mm. 



Occurrence.— On the north side of Mount Diablo in tuff beds just below the 

 San Pablo, associated with Acila gettysburgensis Reagan, Mallelia packardi, n. sp., 

 and Cardium lorenzoanum Arnold. 



Pseudoperissolax merriami is closely related to P. blakei Gabb, 154 

 a characteristic species of the Tejon, the sculpturing and general 

 outline being very similar. P. merriami differs from P. blakei in that 

 the spire is higher, the angulations on the body whorl are farther 

 apart, and there are fewer nodes on the angles. The spiral ribbing 

 on P. blakei appears to be the coarser, and the canal is apparently 

 more elongate and slender. It should be remembered, however, that 

 the anterior portion of the canal on the specimen from the Oligocene 

 is broken. 



153 For Gabb 's original description of Perissolax, see Synopsis of the Mollusca 

 of the Cretaceous formation, including the geographical and stratigraphical range 

 and synonymy, Proc. Amer. Philos. Soc, vol. 8, p. 122, March, 1861. 



154 For original description of Perissolax blakei. see Pacific Railroad Rep., 

 vol. 5, p. 322, pi. 2, fig. 13, 1855. For good redescription of the species, see Gabb, 

 W. M., Geol. Surv. Calif., Palaeontology, vol. 1, p. 92, pi. 21, fig. 110, 1864. 



