Y L D I A 



Species 11. (Mns. Brit.) 



Yoi.DiA LASCEni.AT.\. Yot. testd crassd, subventi-icosd, 

 ohlongo-suhlaiiceolald, siibcompressd, sidcis arniatis 

 ohliquis, s^didistantihus antice et medio sculptd, 

 epidf.rmide valido indiitd ; latere pontico brevius- 

 ciilo, margine dorsali declivi, termino late truncato, 

 ared rostrali Icengatd, leviter radkitim angulnlA ; 

 latere antico ad tenninum rotimdo. 

 The lanceolate Yoldia. Shell thick, .siibventvicose, 

 oblong-sublanceolate, subconipressed, scul[)tured 

 with curved, oblique, rather distant sulci in front 

 and in the middle, covered with a strong epider- 

 mis; posterior side rather short, dorsal margin 

 sloped, end widely truncated, rostral area smooth, 

 slightly radiately angular; anterior side rounded 

 at the end. 

 SowEuiiY. Mineral Conchology, Plate IMI. f. 1. (lbs.sil). 

 Nucula arctica, Broderip and Sowerby. 

 Nueida ceolira, Valenciennes. 

 flab. Kamtschatka. 



The Xucula lanceolata of the Conchological Illus- 

 trations, now Lada SowerUana of D'Orbigny, is quite 

 a distinct shell from this, which was first figured and 

 described from a fossil specimen. 



Spuaes 12. (Fig. a, h, Mut^. Brit.) 

 Yoldia ulacialis. Yol. testd obhmgo-suhqiiadratd, 

 tenui, ventricosd, epidermide olivaceo aut fusco- 

 nigricanti hidutd ; latere poslico late angulato, 

 mperne acuminato, margine ventrali ad tej-minum 

 oblique truncato; margine dorsali mbconcavo, 

 depresso ; umbonibus rotundis, elevatis, margine 

 ventrali medio rectiugculo : latere antico brevi. 

 subrotundo. 

 The glacial Yoldia. Shell oblong-subquadrate, 

 thin, ventricose, covered with an olive or blackish- 

 brown epidermis ; posterior side widely angular, 



acuminated above, ventral margin obli' 

 truncated at the end, dorsal margin slightly 

 cave, depressed ; umboes rounded, rie\ 

 ventral margin rather straight in the m\i 

 anterior side short, rather rounded. 



(Jhav. Annals of Philosophy, ISS.i. 



Nucula truncata. Brown. 



Xucnia Portlandica, IlitclicocU. 



Xucuhi siliqua, Reeve. 



!/(d). Arctic Ocean. 



Spr.'ies l:;. (.Mns. Bvit.l 

 [ATl'LA. Yul. leistd oblungo-lanceolatii, co 



prefxd, epidermide IcFvujato, olivaceo indutd ; latere 

 postico subarciiato, subrostrato, margine dorsali 

 depresso, ared defnitd, termino truncato ; margine 

 ventrali sumilm acclivi ; umbonibus lumd promi- 

 nentibus, margine ventrali wqualifer ronvexo : 

 latere antico subrotundo. 



The polished Yoldia. Shell oblong-lanceolate, com- 

 pressed, covered with a smooth olive-green epider- 

 mis ; posterior side a little arched, subrostrated. 

 dorsal margin depressed, with defined area, 

 end truncated; ventral nun-gin slop. , I iip\\:iiils; 

 uniboe.s not prominent, ventral iiiarLnn i'.|ually 

 convex ; anterior side ratlin- rnunded. 



Sav. (Xucula) Amer. Conch.. ]il. \'>. 



//lib. Maine and Jlas.sachusetts. 



Species 14. (Fig. a, b, Mus. Brit.) 

 Yoldia .MicncA. Yol. testd, compressd, ohlougo-lancro- 

 latd, nitenti, olivaceo, fusco coneentrici' sirigatd ; 

 latere postico subaltenuato, margine dor.tali 

 depresso, ared cou.vexitiscidd, defiuitd, imtrijine 

 centralt suhito acclivi, termino trvncnto : latere 

 antico ad marginem ventralem sinuolo : luuulii 

 convexd vix definitd. 



Lsn. 



