﻿M Y A, 



Plate I. 



Genus MYA, LinncBus. 



Testa (eqvivahis, bimusculosa, pleruvique ad extremitales 

 hiaiis, oblonga, ejndermide riigato indiito. Cardo 

 edentulo, lamina Ugamentifera tritjona, excarata, 

 projecta, in valva sinistra miinito. Impressio pallii 

 pltisminusve sintiata. 



Wiell eqiiivalve, bimuscular, genorally gaping at each 

 end, covered with a wrinkled eplderniis. Hinge 

 toothless, furnished in the left valve with a 

 ligament-bearing, trigonal, hollow projecting 

 plate. Pallial impression more or less sinuated. 



Genus CRYl'TOMYA, Cnrail (Imluded). 

 In the more restrictid genus Al>/ii, typilied Iiy 

 M. arenaria and M. trunrala, the sijihons are long and 

 jiroduced, and covered with a coriaceous e[)!dermis in 

 contintiation of that which covers the shell ; but in 

 «he Cryidomyte there is not the same epidermis- 

 covered projection. But the construction of the hinge 

 and general characters of the shell, and the mud-boring 

 habits of the animal are alike in both groui)s; and no 

 useful purpose is served in keeping thcni apart. The 

 Mijce are few in number, and are principally in- 

 habitants of Northern shores. 



Species 1. (Mus. Sowerby.) 

 Mya akenahia. Ml/a testa ovata, solida,fulv'i, conren- 

 tiici leviter riigatd, utiinque valide hianti ; latere 

 antico ventricoso, lata, latere postico cuneato, sub- 

 depresso, leviter angulato, ad tcrminum subohliqu!' 

 truncato ; lamind ligamentiferd in ralrd rte.iird 

 magna, productd ; impressio ue pallii late et quad- 

 ratim sinnalo. 

 The s.\nd Mva. Shell ovate, solid, brown, concen- 

 trically lightly wrinkled, gaping strongly on each 

 side ; anterior side ventricose, broad, posterior 

 side cuueate, subdepressed, slightly angular, 



rather obliquely truncated at the end ; ligament- 

 bearing plate in the left valve large, produced, 

 pallial impression broadly and squarely sinuated. 



LiNN.EUS. Systema Naturie. 



Hab. British Coasts. 



Species 2. (Mus. Brit.) 



Mya Ei.i.ipiTlCA. j\fi/a tesid Imui, onitd, compressd, 

 anguste hianti ; latere antiro lireriksculo ; latere 

 postico projir iniinjiueni (liirsalein oblique depressd, 

 angulatd, ad tcniiininn uhliquH truncald ; margine 

 vcntrnli rertiitfci'lo. 



The elliptical Mva. Slui' thin, ovate, compressed, 

 narrowly gaping ; anterior side rather short : 

 posterior side obliquely depressed near the dorsal 

 7uargin, angular, obliquely truncated at the end ; 

 ventral margin rather straight, 



A. Ai.A.MS {('ri/ptuinya). MS, Mus. Brit. 



ILdj. .' 



More nearly equal-sided than ^[l|n C'<difornica, the 



anterior and not the posterior side being the shorter. 



Species 3. (Fig. a, h, Mus. Brit.) 



Mya Californica. Ifya testd compressd, anguste hianti, 

 ovatd, pallide rubescenti ; latere antico inflato, 

 rotuiido, umhonibus sabretrorsis ; latere postico sub- 

 angustato, breviiisculo, ad termiimm subtruncato, 

 lamind ligamentiferd parviusculd, sinu pallii im- 

 pressionis parvd. 



The Californian Mya. Shell compressed, narrowly 

 gaping, ovate, pale reddish ; anterior side inflated, 

 rounded, umboes leaning a little backwards ; 

 posterior side a little narrow, rather short, slightly 

 truncated at the end ; ligamentiferous plate rather 

 small, sinus of the pallial impression small. 



Conrad ? Cri/ptonii/a. 



Hah. California. 



May, 1875. 



