588 GASTROPODA. [Opisthobranchia. 



most specimens there is visible a large bare area down the centre of 

 the back. The rhinophores are distinct, but not large ; entire, not 

 perfoliated or grooved. The white band which runs from them to the 

 mouth appears in some specimens to be a ridge. They point out- 

 wards, right and left, and do not stand vertically. The anal papilla 

 is dorsal, behind the perrcardial prominence, and slightly to the left 

 of it. The genital opening is just behind the rhinophores. The foot 

 is fairly broad, white, truncated in front, not grooved or notched, 

 and not produced into tentacular processes at the corners. Its margins 

 are not expanded at the sides, and it is prolonged into a short flat 

 tail behind the body. (Eliot.) 



Length about 10 mm. ; breadth. 4-5 mm. ; height, 3-3 mm. (largest 

 preserved specimen). The largest cerata are about 3-5 mm. high, 

 with a maximum breadth of nearly 2-5 mm. 



The buccal mass is small, of the shape usual in the genus, and 

 without jaws. In the specimens dissected the radula was consistently 

 composed of 5 teeth in the ascending portion, 8 in the descending, 

 and about 10 in the sac, still retaining a spiral arrangement, though 

 somewhat in disorder. The teeth are as usual in the Ascoglossa : 

 they are rather large, colourless, spoon-shaped, indented in the back, 

 and not denticulate in any part. (Eliot.) 



For further information on the anatomy of the species see Sir 

 Charles Eliot's paper. 



Hab. Lyttelton Harbour, type (Hutton) ; Te Onepoto Bay, near 

 Lyttelton, in a tide-pool (H. S.). 



Remarks. - - This species is allied to the S. bettulus ( = S. Marice) 

 of European waters, but differs in having more cerata and a ridge- 

 like prolongation of the pericardium visible on the back ; perhaps 

 also in the absence of a spine in the genitalia. (Eliot.) 



ORDER 2. PULMONATA, Cuvier. 



Euthyneura with a pallial cavity, but no ctenidium. The pallial 

 aperture is diminished by the fusion of the mantle-border with the 

 neck, and reduced to a comparatively small contractile orifice at its 

 posterior extremity. The pallial cavity and shell are often reduced ; 

 the latter may be partially covered over, or internal, or even absent. 

 There is never an operculum in the adult, except in Amphibola, and an 

 operculum is only found during the development in the Auriculidce, 

 Siphonariidce, and Onchididce, all of which are marine forms. In the 

 pallial cavity the interior wall of the mantle is traversed by vascular 

 arborisations, and thus constitutes a pulmonary organ adapted for 

 breathing air. In the Athoracophoi-idce the pulmonary cavity is pro- 

 longed into fine respiratory canaliculi, and thus becomes a tracheal 

 lung. It is much reduced in the Onchididce. In some rare cases the 

 pulmonary cavity may be filled with water, and then its wall may give 

 rise to a secondary branchia which is not the equivalent of a ctenidium 



