BIVALVIA. 205 



Gen. Char. Shell ovate or oblong, equivalved, inequilateral, somewhat compressed. 

 Hinge composed of three cardinal teeth in one valve, and two or three in the other. 

 Muscular impressions ovate, with a deep palleal sinus. Ligament external. 



Animal oblong ; the mantle closed all round with the exception of a small opening 

 in front for the passage of the compressed and lanceolate foot ; siphons unequal, dis- 

 united at about half their length ; extremities ornamented with a double row of fringes. 



The arrangement of dental characters in what constitutes this genus, as well as 

 the general form of the shell, approach so closely to those of Tapes, that it seems more 

 entitled to a position amongst the Venus family than to any other, and so far as the 

 form of the foot of the animal or its siphons may determine its connections, it does 

 not any further justify a removal ; its habits certainly resemble those of Saxicava, but 

 the selection as a habitat in holes, formed in rocks, is not peculiar to one family, as 

 Bivalves of very different forms have been found located in such situations : and habits 

 alone are not sufficient for the uniting into one family those Bivalves which possess 

 them ; perhaps, after all, this genus as it now stands will be found to possess no 

 sufficient claims for a separate position, and may probably be hereafter united with 

 Tapes. 



As a genus it contains but very few species, and little is at present known respecting 

 its exotic allies in the recent state, and nothing in the fossil of an older date than the 

 Upper or Middle Tertiaries. 



1. VENERUPIS IRUS. Linnaus. Tab. XIX, fig. 6 a, b. 



DONAX IEUS. Linn. Syst. Nat., ed. 12, p. 1128, No. Ill, 1767. 



Poll. Test. Sicil., vol. i, t. x, figs. 1, 2, and vol. ii, p. 83, t. xix, figs. 25, 26, 



1795. 



CUNEUS FOLIATUS. Dacosto. Brit. Conch., p. 204, pi. xv, fig. 6, 1778. 

 TELLINA CORNUBIENSIS. Penn. Brit. Zool., ed. 4, vol. iv, p. 75, No. 35. 

 VENUS IRUS. Brown. Illust. Brit. Conch., pi. xx, fig. 9, 1827- 



RUPESTRIS? Broc. Conch. Foss. Subap., p. 559, t. xiv, fig. 1, 1814. 

 VENEBTJPIS IKUS. Lam. An. sans Vert., t. v, p. 507, 1818. 



Payr. Catal. MoU. Cors., p. 35, 1826. 



Phil. En. Moll. Sic., vol. i, p. 21, vol. ii, p. 20. 



Forb. and Hani. Hist. Brit. Moll., vol. i, p. 156, pi. vii, figs. 1 3, and 



pi. G, fig. 2. 



Midden. Malac. Rossic., p. 567- 

 PETRICOLA IRUS. Turt. Brit. Biv., p. 26, t. ii, fig. 14, 1822. 



RUPESTRIS? Dubois. Coq. Foss. Wolh. Pod., pi. vii, figs. 3, 4, 1831. 

 PULLASTRA IRUS. Brown. Illust. Brit. Conch., 2d ed., pi. 37, fig. 9. 



CAPSA IRUS. "Leach, 1818." Ann. and Mag. Nat. Hist., vol. xx, p. 272. 

 ? Encyc. Method., pi. 262, fig. 4. 



Spec. Char. Testa cmato-oblongd, vel subtrapezoidea, crassd ; posticelongiore et latiore, 

 subangulatd; lamellatd, lamellis transversis, interstitiis radianter striatis ; dentibus tribus 

 in utraque valvd ; sinu pattiari magno, subangulato. 



