Hdcioniscus.\ GASTROPODA. 



87 



7. Helcioniscus strigilis, Hombrou and Jacquinot, 1841. Plate 7, 

 fig. 22. 



Patdla strigilin, H. & J., Ann. Sci. Nat. (2), xvi, 1841, 190. Patinella 

 strigilis, H. & J. : Button, P.L.8. N.S.W., ix, 374. Helcioniscus 

 strigilis, H. & J.. Man. Conch. (1), xiii, 137 ; Suter, P. Mai. S., vi, 351. 



Shell oval, convex, obliquely conical. Sculpture consists of 20-30 

 low radiating ribs, with a short interstitial rib, often obsolete, crossed 

 by distinct concentric growth-lines. Colour blackish-rufescent above, 

 brownish-rufescent below ; very often greenish or grey, with the ribs 

 light brown. Apex at the front third to eighth, obtuse, sometimes 

 whitish. Interior typically blackish-purple, iridescent, sometimes 

 greyish-brown, with brown rays corresponding to the exterior ribs ; 

 central area well defined, cream colour to light brown ; muscle-scar 

 sometimes much raised and tuberculate. Margin broadly denticulate. 



Length, 65 mm. ; breadth, 50 mm. (type). Length, 80 mm. ; 

 breadth, 68 mm. ; height, 39 mm. (specimen from Campbell Island). 

 Length, 64 mm. ; breadth, 51 mm. ; height, 34 mm. (specimen from 

 Auckland Islands). Length, 42 mm. ; breadth, 35 mm. ; height, 

 21-5 mm. (specimen from Preservation Inlet). Length, 60mm.; 

 breadth, 48 mm. ; height, 24 mm. (specimen from Tauranga). 



Dentition. Hutton, T.N.Z.I., xv, 128, pi. 16, f. A (P. magellanica). 



Type in the Mus. Hist. Nat., Paris ? 



# a 5. From Tauranga to the Bluff. Chatham Islands ; Anti- 

 podes Islands ; Auckland Islands (type) ; Campbell Island ; Snares. 



Remark. The elevation of the shell and the situation of the apex 

 are variable, as is also the colouring of the interior. 



SUBORDER 2. RHIPIDOGLOSSA. 



Aspidobranchia with a pallio-visceral anastomosis ; eye with a 

 crystalline lens ; a single osphradium, except in genera with 2 ctenidia ; 

 1 or 2 hypobranchial glands. Mandibles paired, lateral. Radula 

 characterized by (1.) The extraordinary development of the uncini, 

 of which there are so many that they are always reckoned as inde- 

 finitely numerous ; they are long, narrow, hooked, and often cusped 

 at the top, and crowded together like the ribs of a fan, those at the 

 extreme edge not being set straight in the row, but curving away 

 backwards as they become smaller. (2.) The varying number of the 

 laterals ; the average number of these is 5 on each side, varying from 

 3 to 9 ; the lateral next to the uncini is specially large. Taking 5 

 as the average number of laterals, the rhipidoglossate formula of teeth 

 is oo 5 . 1 . 5 oo. Heart with 2 auricles ; ventricle traversed by the 

 rectum, except in the Helicinidce. An epipodial ridge on each side of. 

 the foot, and cephalic expansions between the tentacles often present. 



