MANUAL OF CONCHOLOGY. 



FAMILY TEREBEID^E. 



Shell long, solid, narrow, many-whorled, whorls flattened, 

 suture superficial; the aperture small, notched in front, columella 

 without plaits. Operculum horny, annular, with apical nucleus. 



Animal having the foot rounded in front, elongated behind ; 

 head rather large, with short, small tentacles furnished with eyes 

 at their tips ; between the tentacles extends anteriorly a rather 

 long cylindrical trunk. Teeth subulate, arcuate, in two lateral 

 rows (1-0-1); PL 12, fig. 40. 



The family is now restricted^ the Single genus Terebra (auger- 

 shells), including about 170 living species ; the genus Pusionella, 

 formerly referred to Terebridae, being now included in the Pleuro- 

 tomidae. Troschel, however (Gebiss der Schnecken, ii, 28 ), found 

 so much difference in the mouth-parts of the few species of Tere- 

 bridae examined by him, that he would have separated them into 

 three families, notwithstanding the close relationship of their 

 shells, had he not been deterred by the paucity of material for 

 study. His three types are as follows : 



1. The mouth-mass at the end of the proboscis furnished with 

 arrow-like teeth, as in Conus, and a poison-gland. 



Hastula cserulescens. 



2. No teeth, no venom-gland. Acus muscaria. 



3. The mouth contains a true radula, supported by a lingual 

 cartilage, with two rows of side-teeth ; no venom-gland. 



Myurella duplicate,. PI. 12, fig. 40. 



Finally in examining a specimen of T. subulata (representative 

 of the restricted group Terebra), Troschel only obtained negative 

 results ; seeing no teeth, although the poison-gland was present. 



