Y L D I A. 



Genus YOLDIA, MOlln: 

 Testa hiiitusciilosa, (equivalds, Monga, aiinpnsm, /re- 

 quenter utrinque hians, mtiis niirnn ; laltre jm.itiru 

 hand attemtato ; nargine cardinali nngulato, Ji-n- 

 lil/11,1 utrinque iiMnerosis ; lujitmentu internn. 

 Sliell biiimscular, eqiiivalve, oblong, oompressed, fre- 

 c}ueiitly gaping ;it both ends, pearly within ; pos- 

 terior side not attenuated ; hinge margin angular, 

 the teeth on each side numerous ; ligament inter- 

 nal. 

 The YoUlice have not tiie [)eculiur cuneate form of 

 Xiicula, nur is the posterior side rostrated and produced 

 as in the Lcedw. In many ol' the s[iecies the valves 

 are slightly parted at each end. .\ large projiortion 

 are inhabitants of the northern seas both of Europe 

 and America. 



(Fig- 



Brit.) 



Ydi.Di.-i WooD\v.\Ri)i. Yol. testa ovato-subitfuiidnatd, 

 (iblotii/d, compressd, Iwvigatd, inwquUaterali ; latere 

 jKistico breri, aciiminato, ad terniiiiim truncato, mar- 

 gine dorsali depresso, majyiin c. ntndi mite rostnuu 

 paulu cmcavo ; latere antieo jnodueld, e/liptiin, 

 margine dorsali convexv. 



Wuoinv.-MiD's YoLDiA. Shell ovate-subacuuiinate, nb- 

 long, compressed, smooth, inequilateral : posterior 

 side short, acuminated, tnmcated at the end, dorsal 

 margin depressed, ventral margin a little concave 

 in front of the beak; anterior side produced, 

 elliptic, dorsal mai'gin convex. 



lI.\Ni.i;y. I'roc. Zool. Soc, 1860. 



//.(/.. Falkhind Islands. 



Species 1. (Fig. a, b. <■, Mus. Brit.) 

 I>IA Tmuci.BF 

 nitd, reiitrico! 

 rtdii/o iiiiliitd ; iiittis j, 

 Imjiniferd magnd ; late 



Vol. testd oblioigii-.'^ubqiiad- 



lariijittd : epi',1, miide idivareo 



jiiillidi.<siiiie rosiil, j'lissd carti- 



■o iiiigiiliito, latesnprd. 



;!, a, /., Mus 



Yoi.ni.v 

 lutd 



et infra obtuse trunrato : margine dorsali depresso, 

 subconcavo, area imprcssd, latd, dejinitd : latere 

 antico b?-eriiisailo, subcuneato. 



The Thu.4ci.efokm Y'oldi.\. Shell oblong-subquadrate, 

 very ventricose, smooth, covered with a strong 

 olive epidermis ; very pale rose within, cartila- 

 giniferous pit large ; posterior side angxdar, ob- 

 tusely truncated above and below : dorsal margin 

 depressed, subconcave, impressed area wide, 

 defined ; anterior side rather sliort, rather cuneale. 



Stoker. Boston Journal, vol. ii. p. 1 22. 



Yoldia angularis, Miiller (young.) 



Xucula laternaria, Valenciennes. 



Xucula navicidaris, Couthay. 



Yoldia Mulleri, Gray. 



November 



Yul. testd 

 ;rali,epide. 

 indiitd : h:t 



tide 



area plauulntd, de/iuitd , liitire mitieo jiin/ii: ter- 

 mimim radiidim iiupresso. imiegine reiitndi pnid, 

 concaro. 



The .\i.moxi) Y'oi,di.\. Shell compressed, ovately lan- 

 ceolate, nearly equilateral, covered with a brown 

 or olive rayed, shining epidermis ; posterior side 

 slightly acuminated, truncated at the end, dorsal 

 margin depressed, area flattened, defined ; anterior 

 side radiately im)iressed near the end, with ventral 

 margin a little cou-ive. 



Valenciennes. Zool. Xi^nies Moll. pi. •.';!, I. G. 



Hi(b. Kamtschatka. 



