76 



SYSTEMATIC ARRANGEMENT 



the shell is placed with the aperture upwards or downwards, it does 

 not usually commence creeping by pushing out the foot anteriorly, 



Fig. 44. 



like other Gasteropods, hut often twists the long neck and foot to 

 the caudal extremity, and there fixing it, with a sudden spring effects 

 the turning of the shell. — Clark, Moll. 474. 



Branchial plume single, long, narrow, with ahout forty very short 

 pectinations ; above the plume there is a glandular substance resem- 

 bling the mucous fillets of the Canalifera. — Clark, Moll, 472. 



The shells of Aporrhais are subject to great variety with respect to 

 the outer lip, which increases by age. Young shells have all the 

 appearance of a Murex, without the least expansion of the lip, and 

 all gradations are to be met with from that to the perfect shell. 



The animal of the A. pes-pelecani has a long snout and two filiform 

 tentacula of a pink colour, the former spotted with white. Eyes 

 black, at the base of the tentacula beneath ; sustentaculum short, 

 white. 



2. Strtjthiolaria. 

 Shell ovate; spire conic ; mouth ovate; canal short, indistinct; lips 

 thickened, reflexed and rounded on the edge. Operculum ovate, acute. 



a. Operculum ovate, acute, with a notch below the tip (fig. 45). 



1. S. papillaris. 



(i. Operculum : apex very acute, without any distinct notch. 



2. S. crenata. 



Rostrum of Struthiolaria crenata elongate- 

 conic when alive, when contracted in spirits short, 

 thick, annulated. Tentacles subulate, lateral ; 

 eyes small, on outer side of the base. Lingual 

 membrane thin ; teeth 3 ■ 1 • 3 ; central sub- 

 ovate ; apex truncated, reflexed, entire ; lateral 

 slender, subulate, curved ; apex acute, entire, 

 inner largest. Foot small, oblong. Operculum 

 small, ovate ; apex very acute, solid, transparent, 

 with a broad notch or rather sinuation on the 

 inner side near the tip. 



Fig. 45. 

 Operculum of Stru- 

 thiolaria papillaris. 



