86 ZOOLOGY. 



nacre very brilliant and iridescent. As the animal increases in size a new 

 hole is formed in the shell, and the oldest one is closed. The head is 

 ])roboscidiform, with two long tentacles, each with an oculiferous peduncle ; 

 foot large, provided above with a double membrane scolloped into leaflets of a 

 very ornamental character. The water is admitted to the branchise through 

 the holes in the shell, which also allow certain filamentous appendages of the 

 mantle to protrude through them. There are two pectinated branchiae. The 

 genus Stomatia is allied to Ilaliotis, but the shell has no perforations. This 

 sub-family was included by Cuvier among the Aspidobranchia, but Deshayes 

 assigns good reasons for placing it among the Ctenobranchia. 



Neritina {N. fluviatiUs^ i)l. ^i^^fig. 87) is a genus of small sub-globular 

 or oval fluviatile shells, with a semi-circular aperture closed by a calcareous 

 operculum. The two tentacles are long, and eac-h is accompanied by a 

 short secondary tentacle, with an eye upon its summit. 



Fam. 5, Pyramidellidca. This is a small family, composed of the genera 

 P]iramidella and Tornatella. 



Fam. 6. JBuccinidm. In Buccinum {B. undatum^ j^Z. 75, fig. 120), the 

 foot is narrow, the head small, continued in a proboscis, with two tentacles, 

 each having an exterior oculiferous peduncle ; siphon protruding ; sexes 

 distinct, the male with a long exterior organ from the right side of the neck ; 

 shell oblong-oval, with a notch anteriorly. The species figured inhabits botli 

 sides of the North Atlantic. The genus has numerous species, both recent 

 and fossil. Nassa and Eburna belong to this family. Ehvima glahrata is 

 an Ancillaria, and Deshayes thinks the remaining species of Eburna should 

 be merged into Buccinum. 



Fain.^. Purpuridcß. This marine family is mostly carnivorous; the 

 water is taken to the branchiie through a siphon, which passes out of the 

 notch or canal at the anterior part of the shell. The eyes and tentacles are 

 two in number, and the ^Droboscis is well developed. The operculum is thin, 

 and much smaller than the aperture, to allow the animal to withdraw some 

 distance within the shell. Cancellaria is placed in this family, although it has 

 no operculum, and lives upon vegetable food. The animal resembles Purpura. 



Purpura lapillus {pi. 75, fig. 118) is about an inch long, and abundant 

 on rocky coasts on both sides of the Atlantic. 



Pleurotoina {P. hahylonia., pi. 75, fi^. 110) is a genus with an elongated 

 spire, a straight canal, and a narrow notch jiosteriorly in the right lip of the 

 shell, corresponding to a notch in the mantle. The species of this genus 

 are numerous, amounting to over a hundred of recent, and more than this 

 number of fossil tertiary species. There have been nearly fifty species 

 described from the tertiary formations of the United States. 



M'wrex {M. ramosa^ pi. 75, fig. Ill ; M. haustellum., fig. 112 ; M. 

 fribulus, fig. 113). Rondeletius and Aldrovandi have treated of this 

 and some allied genera. The genus muTcx of Linnaeus was founded in 

 1758, but Rondeletius had named several of the species purpura., under 

 the belief of their being the purpurae of Pliny, wdiich were supposed to 

 furnish the purple of the Tyrians. The shell named Murex by Pliny and 

 Kondeletius, belongs to the modern genus Stromhus. Murex is a genus of 

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