SOLENOCONCHIA. 185 



SOLE'NOCONCHIA*, (SOLE NO- 

 CONCHES) Lacaze-Duthiers. 



Body cylindrical, gradually tapering to a rather fine point : 

 mantle sheath-like, contractile, thickened in front, where it 

 forms a circular collar, thin and membranous in the middle, 

 constricted behind and terminating in a short tubular process : 

 head small and indistinct, not visible outside, furnished with 

 a pair of horny jaws and a spinous tongue : mouth internal, 

 surrounded by labial palps : tentacles thread-shaped, long and 

 numerous, arranged in two bunches, one on each side of the 

 mouth; they are contractile and ciliated: gills rudimentary 

 and obscure, placed above the liver : foot remarkably flexible, 

 and divided into three lobes, the middle one of which is conical 

 and extensile ; it occupies the front and issues from the collar 

 of the mantle : posterior tube serving the purposes of a branchial 

 and excretory duct, as well as assisting in the work of repro- 

 duction. 



Shell tubular and resembling an elongated funnel, more or 

 less curved, and open throughout, with the broader end in 

 front ; the narrower or posterior end is channelled and some- 

 times slit. 



This small eccentric class comprises the "tooth shells/'' 

 so called from their resemblance to the tusks or canine 

 teeth of some animals. Their nature in a zoological 

 point of view was but little understood until of late 

 years. Linne placed them in his " Vermes. Testacea ; ,} 

 Lamarck and Cuvier considered them Annelids ; De 

 Blainville and Deshaves restored them to the rank of 

 Mollusca. But the skilful and patient investigations of 

 Lacaze-Duthiers have at last solved a problem the interest 



* From the tube-like shell. 



