A\(\ MO I, I, use A. 



r.vcr, an; waiiliiii;, uinl Uic, anterior muscular impression is not so 

 lonjj(l). The ^c.uuH 



Vknus, I /hi. 



Comprises many 'I'estacca whose }j;en«'.ral character consists in the 

 teetl» and plates of the hin^je bein^; approximated under the summit, 

 in a sinfjie group. They are usually more llattetied and elongated, in 

 a rlirection |)arallel to the hinge, than the Cardia. 'I'he ribs, when 

 there arc any, are almost always parallel to the edges, being directly 

 the reverse of their arrangement in the Cardiu. 



The ligament fre(|uently leaves an elliptical iiiiijrcssiori Ijchlnd the 

 summits, which has received the, appellation ol" vn/vii, and before 

 these, same summits there is almost always an oval impression lenii- 

 ed the dui/x or lunnUti^'i). 



'I'he animal is always furnished with two metre or less j)rotrac.lile 

 tubes, sometimes united, and with a compressed foot, wiiich enal)le, 

 it to crawl. 



M. Lamarck, approjjriates the name of Vknus to those wl»ich huve 

 Ihree small diverging teeth under the summit. This character is 

 particularly well marked in the. (jblonp; and slightly convex. sj)C- 

 cie8(;]). 



Some of them — the AsiAuiyi;, Sowerb., or ('uassin^i'., Lam., — have 

 oidy two diveiging teeth on the hinge, and ap()roacii the Crassalella; 

 in their thicktu'ss and some other characlers(4). 



Among the cordiform species, that is, those which are shorter 

 and have more convex nates, and with more closely apjjroximated 

 teeth, we should remark thoH<; where the plates or transverse strix 

 terminate in crc8t8(5) or tul)ero8ities(f)), and those tliat have longi- 

 tudinal ribs and crests elevated behind. 



(1) f/ii^nliiia /ruin.sviriiii, Kiiin., Howcrh., Cien. of HIkIIh, No. X. 



(!2) 'I'iicwe f'untiiKlic. :i|i|)cll:i11()nH of" vulvii uiid iintin, liiivc prol):il)ly r.iiiiHcd tiic 

 extremity of lli<- hIicII, which correHpoiidH to llic ti'uc uiiuh of" llic .'iniiiial, to Ijc 

 Htylcd tlic uiitcrior, mid tliiit wliere llie mouth ix situutcd, tlic; (iOHtcnor. Wc 

 have rcHlored to thcHc cxlrcmiticH tlicir true denominations. Wc must recollect 

 that tlic ligament iw always ixi llic poHtcriursidc of tlic HiimmitH. 



(3) l^cnuH til krutn, Chcmi\.,\l\, xli; — F. rohmdit, II)., xlii, 441; — r. Icxtilisy 

 11)., 44'Ji — F. dcr.icHmita, xliii, A^G, he. 



(4) Venuii mittiiti, Hans l.crin, VIII, tal). '2, f. 3; — (!rnnninii. (/(uiinoniaMistljum.; 

 and iiinonjctlif foHrtii HpicirH, ,//n(. liiiii/<i, Sower., JMin. (Joncli., II, jii. 1,57, f. 1; — 

 Jht. (tsiniilil, l.ajoiikiTc, Soc. d'Hint. Nat. <U: I'ari.s, I, tal). 6, f 1. 



(.O) rniuM i/i/Hi rii, (;iicmn., VI, '27, '2'JV; — ytii. pllmlti, llne.yc- pi. 273, .'!, n, li. 

 —'Vcn. crihinu/iai, ll)., f". 4, 5, b. 



(6) yntuii jmt ij)i rn, Kncyc, 27ii; — I'm. roi/iis, I, am., Kiicyc. |il. 27i>, f. 4. 



