346 



REVISION OF THE NEW ZEALAND PATELLID^, 

 WITH DESCRIPTIONS OF A NEW SPECIES AND SUBSPECIES. ' 



By Henry Suter. 



Read \&th June, 1905. 



Genus HELCIONISCUS, Ball, 1871. 



Helcioniscus, Dall : Amer. Journ. Conch., vol. vi, p. 227 (type, 



Patella variegata, Reeve). 

 Helcioniscus, Pilsbry : Man. Concli. (I), vol. xiii, pp. 80, 123. 



1. Helcioniscus benticulatus (Martyn). 

 Patella denticulata, Martyn: Univ. Conch., vol. i, t. Ixv (1784). 



,, imiricata, Reeve: Conch. Icon., vol. viii, fig. 93 (1855), not of 

 Linne. 



„ Reevei, Hutton : Man. N. Zeal. Moll., p. 108 (1880). 



,, margaritaria, Martens : Crit. List. N. Zeal. Moll., p. 36 (1873), 

 not of Chemnitz. 

 Helcioniscus denticulatus, Pilsbry: Man. Conch. (1), vol. xiii, p. 138, 

 pi. Ixviii, figs. 23, 24 ; pi. xxi, figs. 49, 50 (1891). 



The shell is mostly, but not always, elevated ; one of my specimens 

 has an altitude of 9 mm. only, with a length of 38 mm. The number 

 of principal costae varies from 22 to about 30, and they are imbricated 

 or nodulous, but this character is very often lost in adult shells 

 through the dissolving action of the water. The colour varies from 

 light grey with brownish ribs to dark brown. Interior : The central 

 area is always orange brown, the muscular scars in adult specimens 

 bluish white and slightly raised. The yellowish spots on a chestnut- 

 brown ground are marginal or extending up to the muscle-scar. 



Dentition. The inner lateral tooth has a simple long cusp, and the 

 oiiter lateral has one denticle on the outer edge. The dentition of 

 P. denticulata published by Hutton (Trans. N. Zeal. Inst., vol. xv, 

 p. 128, pi. xvi, fig. B) is that of P. ornata, Dillw. 



Hab. — This species is very local in its distribution, but plentiful 

 where it occurs. In Cook Strait it is common near Lyall Bay. 

 Dunedin and Chatham Islands are mentioned by Capt. Hutton. 



2. Helcioniscus tramosericus (Martyn). 

 Patella tramoserica, Martyn: Univ. Conch., vol. i, pi. xvi (1784). 



,, Diemenensis, Philippi : Zeitschr. f. Malak. (1848), p. 162. 

 ,, variegata, Reeve : Conch. Icon., vol. viii, pi. xvi, figs. 'dHa—c. 

 ,, antipodum, E. A. Smith : Voy, Erebus & Terror, Moll., p. 4, 

 pi. i, fig. 25 (1874). 

 Helcioniscus tnelanostomus, Pilsbry: Man. Conch. (1), vol. xiii, p. 151, 



pi. xxxii, figs. 67-69 (1891). 

 Jielcioniscus tramosericus, Pilsbry: I.e., p. 142, pi. Ixx, figs. 49-52. 



