SAXICAVID^. 135 



Saxicava, Bellevue, 1802. 



JEtym. — Sax2ivi, stone ; cavo, to excavate. 



Syn. — Byssoiii3^a, Cuv., 1817. Rhomboides, Bl. Hiatella, 

 (mmu^a), Daud., 1799. Biapholius, Leach. Arcinella (carinata , 

 Phil. Clotho, Faujas Saiut-Fond, 1807. 



Distr. — 12 sp. Universal. Fossil; Jurassic, Cret. ? Tert. — . 



Shell when young symmetrical, with two minute teeth in each 

 valve ; adult rugose, toothless ; oblong, equivalve, gaping, liga- 

 ment external ; pallial line sinuated, not continuous. 



Animal with mantle-lobes united and thickened in front ; 

 siphons large, united nearly to their ends, orifices fringed ; pedal 

 opening small, foot finger-like, with a byssal groove; palpi small, 

 free ; gills narrow, unequal, united behind and prolonged into 

 the branchial siphon. 



Five genera and fifteen species have been manufactured out of 

 varieties and conditions of the Protean H. 7'ugosa, Linn, (cv, 91, 

 92). It is found in crevices of rocks and coi'als, and amongst 

 the roots of sea-weed, or burrowing in limestone and shells; at 

 Harwich (England) it bores in the cement stone (clay iron-stone), 

 at Folkestone in the Kentishrag,and the Portland stone employed 

 in the Plymouth Breakwater has been much wasted by it. Its 

 crypts are sometimes six inches deep (Couch); they are not 

 quite symmetrical, and like those of the Lithodomus,are inclined 

 at various angles, so as to invade one another, the last comers 

 cutting quite through their neighbors ; they are usuall}'^ fixed by 

 the byssus to a small projection from the side of the cell. The 

 Saxicava ranges from low-water to 140 fathoms ; it is found in 

 the Arctic seas, where it attains its largest size ; in the Mediter- 

 ranean, at the Canaries, and the Cape. It occurs fossil in the 

 Miocene tertiary of Europe and in the United States, and in all 

 the glacial deposits. 



Sometimes they do considerable damage to sea-walls. In the 

 young state, Saxicava rugosa gapes at the superior margin, and 

 the hinge is composed of a small tooth in the right valve, and 

 two rather larger oblique teeth in the left valve ; in this condi- 

 tion it is the Hiatella of Daudin, and the Arcinella carinata of 

 Philippi. 



" Successive generations will occupy the same hole. The last 

 inhabits the space between the valves of its predecessor. In this 

 way four or five pairs of shells msiy be frequently seen nested one 

 within the other, and not unusually a Sphenia Binghami in the 

 centre of all. Cailliaud observed a Saxicava within a specimen 

 of Venerupis Irus, which it had perforated." — Jeffreys, Brit. 

 Conch. 



PARAMYA, Conrad, 1860. (Myalina, Conrad, 1838, not Kon- 

 inck.) Shell subovate, inequilateral, ventricose over the umbonal 

 slope, slightly flattened from beak to base ; surface with irregular 



