MOLLUSCS. 



281 



and iiiij)k'inc'iits oi the former iiiliahitatits. In these heaps on tlie coast of Maine, the 

 bones of the now extinct great auk Lave been foiiuil. 



However eaten, whether raw, or in a chowder, or fried, the ehnn is o-ood, but best 

 of all is the clam-bake, where a long-continued fire heats the rocks red hot. Then the 

 cinders and ashes arc swept away, a thin layer of rock-weed is laid on the hot stones, 

 the clams placed in the centre and covered with more of the rock-weed. The steam 

 generated cooks the clams in the most perfect manner. 



A second species of Jli/a, M. truncata, occurs on our coast, and but one other is 

 known in the world. 3{>/a truncata, instead of being rounded at both extremities, is 

 truncated behind, while in the living specimen the epidermis is extended in the shai)e 

 of a tube, some six (u- seven inclies in length, from the posterior edges of the shell. 

 This species lives below low-water mark, and is not connnon south of Easti)ort. On 

 the P^nglish shores it is more connnon than 3Iija arenaria. 



The species of Saxicava bore into hard mud, stones, etc., and have very irregular 



and greatly distorted shells, so that specific limits are far from certain. Probably our 



,,_ only species is that figured, Saxicava arctica, but several others 



^"^^ have been described upon the variations of this form. Indeed, 



(■'sj^^ j Woodward states that no less than five genera and fifteen species 



"~^ -~^ have been made upon the form known as jS. ruf/osa, and since this 



' ,„,,,,,„ •I'l'l »'^'- arctica are probably the same, the sj-nonymy of this protean 



species is something awful to contemplate. In places where lime- 

 stone is abundant, Saxicava bores holes in it to the depth of about six inches, and as 

 it is not at all careful where it goes, it 

 not infrequently cuts across the burrow 

 of another individual. When a specinu^n 

 dies the soft pai-ts decay, but the valves ;• 

 remain in the burrow, and another iudi- ' 

 vidual occujiies the same burrow, sealing " 

 itself "between the valves of its prede- 

 cessor. In this way four or five pairs of 

 shells may be frequently seen nested one 

 within the other." 



Panopcea is a genus of large shells, 

 the animal of which closely resembles 

 Saxicava. Panoprpa itorvfrjica is a boreal species, specimens of which are occasionally 



found in the stomachs of 

 fishes; the shell is covered 

 with a thick ejjidermis. 



Glycimeris siliqua is the 

 I inly species of the genus 

 known, and jiresents several 

 noticealile peculiarities. It 

 is covered with a thick, 

 glossy - 1 il ack e ]> i d c r m i s, 

 while the interior of the 

 thick valves is rendered 

 very irregular liy the great deposition of calcareous matter seemingly without rhyme 

 or reason. The animal is much larger than the slu'll, and the soft jiarts cannot be 



Fig. 307. — Glycimeris siliqua. 



