vulsellidjE. 523 



In the shells of this genus, which are found at the Mau- 

 ritius and in Australia, there is an umbonal shelf for the 

 support of the anterior adductor muscle, as in Dreissena. 



Species of Septifer. 



bilocularis, Linn. Grayanus, Dkr. 



crassus, Dkr. Herrmannseui, Dkr. 



Cumingii, Becluz. Kraussii, Kiist. 



excisus, Wiegm. Troschelii, Dkr. 



Forskalii, Dkr. virgatus, Wiegm. 

 furcatus, Dkr. 



Fam. VULSELLID.E. 



Anterior adductor muscle none. Gills narrow, much 

 produced behind, united together and to the inner surface 

 of the mantle, dividing the mantle-cavity into two parts. 

 Rectum simple; vent free, medial. 



Genus VULSELLA, Humphrey. 



Shell longitudinal, sub-equivalve, irregular; beaks equal. 

 Hinge with a prominent cardinal callus, depressed above, 

 in each valve, furnished with a conical, obliquely-arcuated 

 pit for the ligament. 



Syn. Reniella, Swainson (young). 



Ex. V. lingulata, Linnaeus, pi. 122, fig. 4, 4, a. 



The species of this genus are inhabitants of the 

 Australian seas, the Indian Ocean, and the Red Sea, and 

 are usually found imbedded in sponges. Extinct examples 

 have been discovered in the Upper Chalk of Britain and 

 France. 



