21 S CALIFOUNIA ACADr.MY OF SCIENCES. 



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



Zirtn*;.— Drake's B:i\ to San Diego, 20 to 30 fathoms (Dall): San Pedro 

 (Raymond). 



PU'hlocene. — San Pidro (.\rrinid). 



197. Cancellaria tritonidea (lulih. 



1'i.ATK VII, Fni. r.. 



Cancellaria irilonidea Gabr, Pal. Cal., Vol. II, \>\>. 11, 79, PI. II, tig. 18, i86g. Cooper, jtli Ann. 

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

 1891, p. 183. 



Shell large, robust-fusiform; spire elevated, subacute; whorls si.\, 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 described in this paper is the largest and most nearly 

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

 not as well jireserved 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 C. cassidiformis Sowerby,an(l it may 

 be one form of this hitter variable species. 



The j^oung 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 (he 

 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. 



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

 Pedro; Ventura (Arnold). 



