from the Vancouver District. 425 
moored by byssus, like Modiola. The largest known species is 
A, falcata, Gld., which is normally straight, but often grows in 
a twisted burrow. A. parasitica, Desh., and the long-known 
A. cinnamomea appear congeneric. 
18. Adula stylina. 
A, testa cylindracea, lithophagoidea, levi, tennissima, parum ar- 
cuata, subnacrea, albida, postice interdum livido tincta; epider- 
mide nitente, levi, solidiore, nigro-fusca: testa jun. typice modio- 
leeformi, umbonibus subanticis, obtusissimis ; margine dorsali 
antice (rarissime paululum, testa minima, postice) tenuiter crenu- 
lato: testa adulta marginibus dors. et ventr. fere parallelis, ant. 
et post. rotundatis; umbonibus detritis, haud conspicuis, circiter 
sextantim antice sitis ; mcrustatione haud solida, densissime spon- 
giosa, aream posticam diagonalem tegente, supra valvas prolongata, 
appressa ; ligamento interno, postice valde prolongato; pagina 
interna pallida; cicatr. add. postica tumida, pyriformi, antica 
(quoad familiam) maxima, haud impressa, oblonga; cicatr. pedali 
antica magna, circulari, impressa; callositate subumbonali (testa 
jun.) cicatr. pedalem versus conspicua. Long. °155, lat. °4, alt. °5. 
Variat t. magis arcuata; ut in 4. falcata, antice tumidiore, sub- 
angulata. 
Variat quoque testa attenuata. 
Variat interdum ventraliter late hiante. 
Hab. Necah Bay, abundant (Swan) ; Monterey (Taylor). 
On smashing a large lump of hard clay, bored by Pholads, 
Petricolids, &c., large numbers of this species, with a few of A. 
falcata, of all ages from 06 onwards, were found in situ. Several 
struggled for room in a single crypt. The umbos are abraded 
by the wide opening of the valves. 
14. Avxinea (?septentrionalis, var.) subobsoleta. 
A. testa’ A. septentrionali simili, parum ineequilaterali, haud tumida; 
umbonibus obtusis, latis, satis prominentibus ; cinerea, rufo-cas- 
taneo varie picta; epidermide copiosa, sublaminata; marginibus 
ventrali et postico valde rotundatis, antico parum producto, dor- 
sali recto; sulcis radiantibus subobsoletis sculpta, dorsaliter seepe 
evanidis : intus, marginibus ventrali valde, ant. et post. parum cre- 
natis ; lamina car dinis subangulata ; dentibus paucicribus, validis, 
angustatis ; cicatr. add. antica castanea, callosa; ligamento sul- 
cato. Lone. °13, lat. -12, alt.°7. 
Hab. Neeah Bay (Swan) ; Shoalwater Bay (Cooper). 
Middendorff’s shell is figured with much stronger ribs, but 
may have been described from decorticated specimens. 
15. Stphonaria Thersites. 
S. testa parva, tenui, haud elevata, valde ineequilaterali, dense nigro- 
castanea, levi, seu interdum costulis paucis, obtusis, obsoletis, 
