ASTRA LI I'M. v>4:l 



The synonyms are Trockus cooksianus etc., Chemnitz, T. cook!! 

 Omel. and of most authors, Cookia nohl/ls Lesson. 



This species frequently exceeds the above dimensions. 



Var. i > A VISIT Sto we, 1871. Unfigured. 

 Whorls keeled at the periphery. 



Muid !!!/, N. Z. 



Subgenus POMAULAX Gray. 1850. 



Shell large, conic, solid, imperforate ; periphery carinated ; base 

 flattened ; umbilical tract with a strong curved rib ; operculum ob- 

 ovate, narrower toward the proximal extremity, nucleus terminal, 

 outside with four strong granulose ribs radiating from the nucleus. 



Japonic and Californian Provinces. 



A. UNDOSUM Wood, 1828. PL 58, figs. 69, 70. 



Shell large, conic, imperforate, white, covered with a strong ob- 

 liquely lamellose corneous epidermis ; whorls 6-8, planulate, with 

 oblique radiating tuberculate costse above ; periphery with an un- 

 dulating nodose carina; base flattened, with three to five concentric 

 corrugations ; aperture subovate, very oblique, angular, pearly with- 

 in ; columella dilated, with a semicircular groove at the position of 

 umbilicus, the umbilical tract bounded by a white grooved ridge. 



Alt. 80, diam. 110 mill. California. 



Operculum (pi. 59, figs. 18-20) obovate, slightly convex inside, 

 nucleus terminal ; outside white, with four strong curved sharply 

 grauulose ribs radiating from the apex. 



T. gigas Anton, and T. balcena-mm Val. are synonyms. 



T. rutilus C. B. Ad. is said to be a very young worn shell of this 

 species. 



Specimens of this shell frequently attain much larger size than 

 the dimensions above given. I have seen specimens of 130 mill. alt. 

 135 mill. diam. Very large examples sometimes become rounded 

 at the periphery, and acquire corrugated sculpture upon the last 

 whorl, quite similar to that of A. sulcatum Mart. 



A. JAPONICUM Dunker, 1845. PL 58, figs. 63, 64. 



Shell large, depressed-conic, imperforate ; pale yellowish ; whorls 

 6, planulate above, obliquely tuberculate-plicate ; periphery expand- 

 ed, compressed, carinated, bearing wide nodose spines ; base plauu- 



