from the Vancoui'cr D'mtrict, 8 



monrcrl by bys'^us, like Mud'wiu. Tlie largest known gperifs is 

 A.falcatu, Gld., which is iionnally straiglit, but often grows in 

 A twisted burrow. J parasitica, Desb., and the loug-kuowa 

 A. cinnaniumea appeal 'igeneric. 



J.J. Adnla stijVma. 



A. testa cyliiulracea, llthophagoidea, lievi, tenuissima, parum ar- 

 cuata, subnacrea, aliiida, postice iuterdum livido tiiicta ; epicler- 

 niide niteiite, Isevi, solidiore, iiigro-fusca : testa jiin. tvpice tnodio. 

 Jeeforiiii, unil)onil)U'i stibantieis, ohtusissimis ; marline dorsali 

 antice (rarissinie |)auhilu;i!, testa iniiiiiiia, postice) tenuiter cienu- 

 lato : testa adulta niargiiiilius dors, et ventr. fere paiMlUlis, aiit. 

 pr. post, rotiuulatis ; uiiil)oiiil)ns detritis, baud coiKpicuis, cireiter 

 sextantitn antice sitis ; iiicriistatioue baud solida, deii>issime spon- 

 giosa, aream posticain (bjigonalein ttj^ente, supra valvas prolongata, 

 appressa ; liajameuto interno, postice valde jjrolongato ; |)a!:iiia 

 interna pallida ; eicatr. add. postiea tuinida, pyritoriiii, aiitica 

 (qufiad faiiiiliaiii) maxitna, baud iinpressa, olilonga ; eicatr. pt-dH'i 

 autica magna, circulari, inipressa ; callositate snljunii)onidi (testa 

 jim.) eicatr. pedalem versus couspieua. I^ong. •If).'), lat. A, alt. '.i, 



Variat t. magis arcuata ; ut '\n A. fulcata, autice tumidiore, sub- 

 angidata. 



Variat qunquie testa attenuata. 



Variat interdum ventraliter late biante. 



Hab. Neeab Bay, abundant {Swan) ; IMontcrey {Taylor), 



On smashing a large lump of hard clay, bored by Pholads, 

 Petricolids, &c., large numbers of this species, with a few of A. 

 falcuta, of all ages from OG onwards, were tound in sitti. Several 

 struggled for room in a single crypt. The uuibos are abraded 

 by the wide opening of the valves. 



14. Axinaa (iseptentrionalis, var.) suhohsoleta. 



A. testa A. septentriovali sirnili, paruui insequilaterali, baud tumida; 

 umbonibus obtusis, latis, satis prominenliljus ; ciuerea, rufo eas- 

 taneo varie picta ; epidermide copiosa, sublaiiiiiiata ; marginibus 

 ventrali et postico valde rotundatis, autico j)arum producto, doi- 

 sali recto ; sulcis radiantibus subobsoletis sculpta, dor>aliter ^a'JJe 

 evanidis : intus, niarginibus ventrali valde, ant. et post, parum cre- 

 natis ; lamina cardinis subangulata ; dentibus paucioribus, validis, 

 angustatis ; eicatr. add. antica castauea, callosa ; ligamento si\".- 

 cato. Long. '13, lat. '12, alt. •/. 



Hab. Neeah Bay {Sivan) ; Shoal water Bay {Cooper). 



Middendorff's shell is figured with much stronger ribs, but 

 may have been described from decorticated specimens. 



15. Siphonaria Thersites. 



S. testa parva, tenui, baud elevata, valde insequilaterali, dense nigro- 

 castanea, locvi, seu interduni costulis jtaucis, obtusis, obsoletis, 



237 



