257 



FAMILY DOLIID^E. 



Shell thin, ventricose, ovate or subglobose, spire short, the 

 body-whorl very large, with revolving ribs or decussated. No 

 opereulum in the adult. 



Animal very large ; the mantle dilated ; head wide, bearing two 

 elongated distant tentacles, dilated at the base, and having eyes 

 near the base ; proboscis cylindrical, greatly developed, extensi- 

 ble and flexible ; foot lobed and dilated in front, with a horizontal 

 groove. 



Dentition. Central tooth short, wide, with an elongated 

 central and some shorter lateral cusps, lateral and first marginal 

 with simple or denticulated margin, sharp-pointed, outer marginal 

 tooth sharp, simple (PI. 1, fig. 1). Jaw (PL 1, fig. 2), 



Some species at least, of Macgillivrayia, are known to be the 

 larva of Dolium. They have four tentacles, and the foot is pro- 

 vided with a float resembling lanthina ; the shell has a thin, 

 corneous operculum, afterwards lost. 



The family resembles Cassididse rather closely, but differs by 

 the want of varices on the shell 'and the absence of an opercu- 

 lum ; but the subgenus Malea of this family, having a ringent 

 mouth, has much analogy with C3'prsecassis of the Cassididse, 

 which, according to Stutchbury, is equally deprived of an oper- 

 culum. The family Oocorythidse, containing a single species, 

 may be placed between the two ; it is in shell characters essen- 

 tially an operculate Dolinm. Prof. Morch and others place the 

 Tritonidie in intimate relation with the foregoing families on 

 account of a similar dentition ; and Morch points out that certain 

 species of Triton possess the revolving ribs and somewhat of the 

 form of Dolium. Oocorys itself is thought by Fischer to be 

 somewhat closely allied with Tritonid?. The relations of Triton 

 with Murex are also evident. Thus it is that transition forms, 

 and complex relationships everywhere baffle the naturalist who 

 attempts to classify in a lineal series. The shells are mostly of 

 quite large size, and the species are few in number, inhabiting 

 warm seas ; fossil, a cretaceous form is known, with some tertiary 

 species. 

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