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. — Aporrhais pes-pelecani. 



like other Gasteropods, but 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 about 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. Struthiolaria. 



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. 



/3. Operculum : apex very acute, without any distinct notch. 



2. S. crenata. 



Rostrum of Struthiolaria crenata elongate- Fig- 45. 



conic when alive, when contracted in spirits short, Operculum of Stru- 



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. 



thiolaria papillaris. 



