218 CALIFORNIA ACADEMY OF SCIENCES. 



Rare in upper San Pedro series of San Pedro; one specimen found. 



Living. — Drake's Bay to San Diego, 20 to 30 fathoms (Dall): San Pedro 

 (Raymond). 



Pleistocene. — San Pedro (Arnold). 



197. Cancellaria tritonidea Gabb. 



Plate VII, Fig. 5. 



Cancellaria irilonidea Gabb, Pal. Cal, Vol. II, pp. ii, 79, PI. II, fig. 18, i86g. Cooper, 7th Ann, 

 Rept. Cal. St. Min., 1888, p. 231. Dall, Proc. U. S. Nat. Mus., Vol. XIV, 

 1891, p. 1S3. 



Shell large, robust-fusiform; spire elevated, subacute; whorls six, first generally decollated, 

 angulated; upper part of first three and one-half revolutions convex; upper part of lower whorls 

 concave; lower part of all whorls, except body-whorl, generally covered with a lamellar incrus- 

 tation; ten prominent sharp nodes on angle of whorl; whorls ornamented with numerous promi- 

 nent, squarish, spiral ridges between which are less prominent raised lines; incremental lines 

 visible, and some of them which pass through the nodes have the prominence of weak varices; suture 

 appressed, wavy, distinct; aperture subovate; outer lip not thickened; inner lip incrusted; columella 

 rough, twisted, widened, with two prominent plications on the inner side; canal short, wide. 



Dimensions. — Long. 90 mm.; lat. 60 mm.; body-whorl 70 mm.; aperture, not including 

 canal 50 mm.; defl. 75 degrees. 



The shell figured and desci'ibed in this paper is the largest and most nearly 

 perfect one yet found in this locality. Gabb's tyj^e specimen was beach worn and 

 not as well preserved as the one described above, which accounts for the lack of the 

 sharp nodes and more rounded outline of his shell. A specimen in this collection 

 labeled "Cancellaria vetusta Gabb, Pliocene, Ventura" by Dr. Bowers, is of the same 

 species. Whether Bowers' specimen came from the Pliocene or Pleistocene is a 

 matter of doubt. 



Dr. Dall pronounced C. tritonidea near to O.cassldiformis Sowerby, and it mav 

 be one form of this latter variable species. 



The young shells of this species are quite variable in regard to the promi- 

 nence of the nodes, amount of angulation of the whorls, and the shape of the aper- 

 ture. Any one not possessing a series showing the connection between the two 

 extremes might think them different species. C. vetusta is probably a precursor of, 

 if not identical with, C. tritonidea. 



Rather rare in the upper San Pedro series of San Pedro. Found also in the 

 Pleistocene at Barlow's ranch and at old irrigating ditch, Ventura. The specimen 

 figured is from the upper San Pedro series at San Pedro, and is now in the collec- 

 tion of Delos Arnold. 



Pleistocene. — Coyote Creek, Ventura County; San Pedro (Cooper): San 

 Pedro; Ventura (Arnold). 



