ASTRA LIUM. 243 



The synonyms are .Trochns cooksianus etc., Chemnitz, T. cookii 

 'Gmel. and of most authors, Cookia nohilis Lesson. 



This species frequently exceeds the above dimensions. 



Yar. DAVisii Stowe, 1871. Unfigured. 

 Whorls keeled at the perij^hery. 



Blmd Bay, 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 Cafifornian Provinces. 



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



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

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

 oblique radiating tuberculate costa3 above ; periphery with an un- 

 dulating nodose carina; base flattened, with thceetofive concentric 

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

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

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



Alt. 80, diara. 110 mill. California. 



Operculum (pi. 59, figs. 18-20) o'bovate, slightly convex inside, 

 nucleus terminal ; outside white, with four strong curved sharply 

 granulose ribs radiating from the apex. 



T. gigas Anton, and T. baloenarum 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 I'ounded 

 at the periphery, and acquire corrugated sculpture upon the last 

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



A. jAPONicuM Dunker, 1845. PI. 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 planu- 



