274 BUCCINIDvE. 



SHELL oval, spirally sculptured ; base strengthened by an 

 oblique ridge : epidermis, if present, velvety or membranous: 

 spire, short ; body- whorl consequently large : mouth oval : pillar 

 twisted : canal short and recurved : operculum horny, oval, 

 never spiral, increasing by concentric or elliptical layers ; 

 nucleus placed within the edge, at the outer side of the mouth. 



The ' Purpuriferes ' of Lamarck. Adanson noticed that 

 the shell of the male is usually smaller than that of the 

 female, and that the former has a longer spire and more 

 whorls although not so tumid. He included this family 

 and the Muricida in his genus Purpura. Miiller out- 

 bid Adanson by composing his genus Tritonium of the 

 same extensive groups, and throwing Aporrhaidce and 

 Nassidae into the bargain; hisBuccinum is ovrLimn&a. 

 The egg-cases are membranous ; those of Bucdnum are 

 cup-shaped, and piled one upon another like the cells 

 of a honeycomb ; in Purpura they are separate, resemble 

 grains of barley, and are placed upright. Although the 

 lingual riband in all the Rhachiglossata (which com- 

 prise the Siphonobranchiata) is armed with spinous 

 teeth, none of this division appear to have the jaws 

 (cheek-plates or immoveable mandibles, Morch) with 

 which the Tsenioglossata (including the Pectinibran- 

 chiata) are provided. The muscle by which the body 

 is attached to the pillar of the shell in families of the 

 present order is unusually strong. 



Genus I. PUR'PURA*, BMgwfc-e. PL V. f. 1. 



i 



SHELL conic-oval, thick, destitute of an epidermis: spire 

 sharp-pointed: who rls more or less compressed: outer Up tuber- 

 culated withia : pillar flattened, sloping inwards with a sharp 

 edge : canal narrow. 



* The name of a shell-fish from which the Tyrian dye (iroptyvoa] was 

 extracted ; erroneously applied to this genus. 



