ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 2n 



The specimen figured has nine post-niiclefir wliorls. Fossil specimens from 

 tlie post-Plioeone of California attained a much larger si-/e than recent representa- 

 tives of tiie species. A fragment of a s|)ccim(Mi collected at San Diego, consisting 

 of the last four whorls, has a diameter of 2. 'J nun. 



295. Turbonilla (Pyrgiscus) subcuspidata Carpenier. 



PlATK, II, I-'lliS. 2 A.Nl) 2f(. 



Cheninitzia subcuspidata Cpr., Proc. Cal. Ac;ul. Sci., Vol. Ill, 1865, p. 220, No. 670. 



vShell stout, strong, somewhat inflated, whitish to wa.xy yellowish; nuclear whorls three, 

 helicoid, of moderate size, slantingly one-fourth immersed, slightly extending beyond the general 

 outline of the spire on one side; post-nuclear whorls well rounded, the last two somewhat flattened, 

 contracted at base, outcurved and muricated at their summits, traversed by sixteen to twenty very 

 strong, flexuose, more or less irregular axial ribs, which extend strongly upward and render the 

 shoulder subcuspidate and very wavy; these ribs become enfeebled on the last whorl and almost 

 obsolete on the base, extending only very feebly over the well rounded periphery to the umbilical 

 region; intercostal spaces wider than the ribs, undulating, traversed by live to twelve deep spiral 

 striations, which extend less prominently over the ribs and cause the whorls to appear as if they were 

 wound by a series of overlapping bands of varied width; these bands vary in number and con- 

 sequently in width, being fewer and most prominent on the earlier whorls, as are the ribs, later on 

 becoming enfeebled; a very slight groove passes about the periphery of the last whorl and maps out 

 the route for the suture; the spiral sculpture of the entire last whorl is very regular, there being about 

 thirteen subequally spaced stri;e above the periphery and eighteen on tlie base; the sutures are very 

 deep, subchanneled; aperture ovate; posterior angle acute; outer lip moderately thick, rather effuse 

 at base, joining the oblitjue, somewhat reflexed columella in a gentle curve; a faint callus connects 

 the posterior angle of the aperture with the insertion of the columella; by transmitted light a faint, 

 light, revolving band becomes apparent in the peripheral region within the aperture. 



Dimensions. — Long. 6 mm.; diam. 2 mm. 



The specimen figured and described is Dr. Carpenter's tN'pe; it has eight and 

 one-half post-nuclear whorls, and comes from San Diego. Fossil speeimens from the 

 same locality are even more robust. One of seven post-nuclear whorls measures: 

 long. 5.G mm.; diam. 2.1 mm. I'^ouihI in the post-Pliocene deposits of San Pedro. 



Section Pi/rgisculus Monterosato . 



Pyrgisciibis Monterosato, Conch. iMedit., p. 88, 1884. Type, Melania scalaris Philippi. 



Turbonillas with strong axial ribs and lamellate spiral sculpture, having a decidedly sloping 

 shoulder at the summit. 



296. Turbonilla (Pyrgisculus) laminata Carpenter. 



Plate II. Fiu.s. 8 and Sa. 



Dunkcria laminata Cpr., Ann. Mag. Nat. Hist., 3rd Ser., Vol. XV, 1865, p. 396. 



Shell white to dark brown, plain or variously banded; nuclear whorls three, large, tumid, 

 helicoid, slantingly slightly immersed; post-nuclear whorls well rounded, ornamented by twenty-two 

 to twenty-eight strong axial folds, which pass feebly over the well-rounded periphery and base of the 



