246 



THE SEA SHORE 



the expanded lip is drawn out into long finger-like lobes that suggest 

 the foot of a bird. This is a very solid shell, sometimes reaching a 

 length of two inches ; and the animal inhabiting it is carnivorous. 



We have yet some tur- 

 reted shells to deal with, 

 belonging to the family 

 PyramideUidce, but they 

 need not be confused with 

 the preceding groups if 

 carefully examined. In the 

 FIG. 176. Aporrhais pes-pelicani, first place, ^ the aperture of 

 SHOWING BOTH SHELL AND ANIMAL the shell is very small ; 



and the operculum, instead 



of being spiral, as in the turreted shells before mentioned, is imbri- 

 cated or made up of parallel layers denoting that the growth took 

 place on one side only. Another distinguishing feature is seen in 

 the nucleus that small portion of the spire that was developed 

 within the egg which is sinistral or left-handed. In addition to 

 this, the animal has broad, ear-like tentacles, a retractile proboscis, 

 and a lingual ribbon without teeth. 



The British species of this fanii^ belong principally to the 

 genera Odostomia, characterised by a tooth-like fold of the 

 columella; Eulima, containing small, white, polished shells with 

 numerous level whorls ; and Aclis, with little polished shells not 

 unlike Turritella. 



The last family of the Holostomata is the Naticidte, the shells 

 of which are almost globular, with only a few whorls, and a small, 

 blunt spire. The mouth is semilunar in 

 form, and the lip sharp. The proboscis of 

 the animal is long and retractile, and the 

 foot large ; but perhaps the most charac- 

 teristic feature is the presence of large 

 mantle lobes which hide some of the shell 

 when the animal is crawling. In Natica 

 (fig. 155), the typical genus, the shells are 

 somewhat thick and smooth, with a large 

 umbilicus. As the animal crawls a large 

 fold of the mantle is reflected back over 

 the head, completely covering it, and ap- 

 parently obstructing its view; but this is not the case, for the 

 creature has no eyes. Natica is very abundant on some sandy 



Fio. 177. 1. Odostomia 

 plicata, 2. Eulima 

 polita. 3. Aclis supra- 

 nitida 



