acephala testacea. 89 
which the hinge is not prolonged. We must be careful not to con- 
found them with the Vulsellse * * * § . 
Vulsella, Lam. 
A little salient plate inside of the hinge of each side, from one of 
which to the other extends the ligament, otherwise similar to that of 
the Ostrese. By the side of this plate is a notch for the byssus, as in 
the Mallei. The shell is elongated in a direction perpendicular to the 
hinge. 
The most known species inhabit the Indian Ocean f . 
Perna, Brug. 
Several parallel cavities across the hinge, opposed to each other in the 
two valves, and lodging as many elastic ligaments; the irregular and 
foliaceous sliell marked on the anterior side and under the hinge by a 
notch traversed by the byssus. The PerncC were also left by Linnaeus 
among the Ostreae 
Crenatula, Lam. 
The Crenatulae, lately separated from the Pernae, instead of having 
transverse cavities on a broad hinge, are furnished with oval ones on 
the very margin, where they occupy but little of its breadth. The 
byssus seems to be wanting, and they are frequently found among 
sponges §. 
It is thought that we may approximate to the Pernae, certain fossil 
shells, in which the hinge is also furnished with cavities more or less 
numerous, that correspond to each other, and thus appear to have fur- 
nished points of attachment to ligaments : thus those of the 
Gervilia, Defr. 
Have a shell closely resembling that of the Volucellae, but with a 
kind of double hinge, externally with opposed cavities, receiving as 
many ligaments, and internally furnished with very oblique teeth in 
each valve. Their impressions are found along with Ammonites in 
compact limestone ||. The 
* Ostrea vulsella, Chemn., VITI, Ixx, 657, of which the Ostrea anatina, Ib. 658, 
659, is probably a mere accidental variety. 
Mya vulsella, Chemn., VI, ii, 10, 11 ; — V. sponyiarum, Lam., Savig., Eg., Coq. 
pi. xiv, f. 2 ; — V. Mans, Lam., Sav., Ib., f. 3. 
J Ostrea isograoOTM/H, Chemn., VII, lix, 584 ; — O. perna, Ib., 580; — O. legumen, 
Ib., 578 ; — O. epMppium, Ib., Iviii, 576 ; — O. mytiloMes, Herm., Nat. Berl., Schr. 
II, ix, 9. 
§ Ostrea picta, Gm., Chemn., VII, Iviii, 575, or Crenatula phasionoptera, Lam., 
Encyc. Method., Test., pi. 216, f. 2 ; — Crenatula avicularis, Lam., Ann. du Mus, III, 
pi. ii, f. 3, 4 ; — Or. mytiloMes, Id., Ib. f. 1 and 2. See also the great work on Egypt, 
Coq. pi. xii. 
II Gervilia solenoMes, Defr., Blainv., Malac., Ixi, 4 ; — G. pernoMes, Deslonchamps, 
Soc. Lin. du Calvados, I, 1 16. — G. siliejua, Id. Ib., &c. 
