104 MYA. GAPER. 



16. Mya dubia. Doubtful Gaper. 



Pennant , pi. 47 Donovan) pi. 108 Wood, pi. 25. f. 2, 

 3 Dorset Cat. pi. l.f. Ji. 



Shell oval, thin, brittle, opake, light brown, white 

 within, irregularly wrinkled or rugged transversely, with a 

 very large open gape in front, commencing near the hinge, 

 becoming narrower towards the smaller end, and exposing 

 the interior of the hinge and the rudiments of teeth : beaks 

 small, prominent, placed at the larger end : hinge with a 

 small plate or rudiment of a tooth in both valves, projecting 

 Inwards : length not half an inch j breadth about three 

 <|ii alters. 



Imbedded in the hardest rocks. v~ v. 



17- Mya arctica. Arctic Gaper. 



Shell oblong-oval, rather convex, coarse, greyish-white, 

 truncate at the hinge end, and something rounded at the 

 other, where it gapes a little, roughly striate transversely, 

 with the striae approaching to membranaceous ridges to- 

 \vards the back, a little inflected on the front margin : beaks 

 prominent, pointed, close to the truncated end, from which 

 run two raised ridges, one along the back margin, the other 

 obliquely to the outer angle of the front margin, both of 

 .Which are rough or somewhat spinous by the sharp dupli- 

 cature of the transverse folds ; under the beaks also, on 

 the truncated slope, is an oblong striate depression ; inside 

 glossy white, with the margin plain : hinge with a strong 

 projecting spoon-shaped cavity in each valve, the edge of 

 v/hich next the flattened side is a little raised so as to re- 

 semble a small tooth ; from this cavity along the cartilage; 

 margin runs a small hollow groove in each valve, and be- 

 low the hinge on the truncated margin withinside is a' flat- 

 tened space in both valves, in the middle of which there is 

 an oblong cavity : length half an inch 5 breadth more than 

 three quarters. 



A living specimen of this very desirable shell we took 

 from a mass of Sertularia, on the strand at Portmarnock, 

 in Dublin bay. It had for some time been undistinguished 

 in our cabinet, among a parcel of the Solen minutus ; and 

 it is probable that it may in this manner have been over- 

 looked by other collectors, 



Fabrkius 





