ACEPHALA TESTACEA. 425 



susceptible of being greatly elong'ated. It appears that they are cer- 

 tainly furnished with a calcareous tube(l). 



In some of them, as in the Mytili, the summits are at the anterior 

 angle(2); in others they are placed near the middle(3). 



They inhabit the interior of Madrepores, which they perforate. 



Two genera of Acepbala furnished with tubes, have been 

 detected among fossils, but the first of them, the 



Tehedina, Lam., 



Has a little cuilleron on the inside of each of its valves, and a small, 

 free, shield-shaped piece on the hinge(4). In the second, 



Clavagella, Lam., 



One of the valves is clasped by the tube, leaving the other, however, 

 free(5). 



A single living species is found in the Madrepores of the Sici- 

 lian seas, which has been described by M. Audouin. 



Some naturalists think we'should also place in this family 

 the 



Aspergillum, Lam., 



The shell of which is formed of an elongated conical tube, closed at 

 its widest extremity by a disk perforated with numerous small tu- 

 bular holes J the little tubes of the outer range being longest, form a 

 kind of corolla round it. The reason for approximating them to 

 the Acephala with tubes is found in the fact that there is a double 

 projection on one part of the cone which really resembles the two 

 valves of the Acephala. The affinity between these little tubes 

 and those which envelope the tentacula of certain Terebella, for- 

 merly caused this animal to be referred to the Annelides. 



The species most known, Asper. javannm, Mart., Conch., I, 

 pi. 1, f. 7, is seven or eight inches in length(6). 



(1) This tube has been observed by Messrs Turton, Deshayes, and Audouin. 

 ^ ^. (2) Fholas Mans, Chemn., X, clxxii, 1678, 1679. 



(3) Id., 1681, a veiy different species from the preceding-, not properly distin- 

 guished by Chemnitz. 



(4) Teredina personata. Lam., and Desh., Foss. de Par. I, pi. i, f. 23, 28. 



(5) CI. echinata, Lam., Ann. du Mus., XII, xlii, 19, CI. coronata, Desh., Foss., I, 

 V, 15, 15. 



(6) Add the Arrosoir a mancheftes, Savig., Egyp., Coq. pi- xiv, f. 9. 



Vol. II. 3 D 



