98 CRETACEOUS PELECYPODA 



right and only one in the left valve, they coukl form the basis of a generic distinc- 

 tion. Bunker (Proc. Zool. Soc, 18G1, p. 425,) describes several new species of 

 Azor. 



14. Cleiclophorus, Hall, 1850, (Pal. New York, ii, p. 300), has been proposed 

 for a palaeozoic form, which in external character resembles Solecurtus and Azw, 

 but nothing is known of the hinge. 



15. Tagehis, Gray, 1847, fSiliquoria, Schuhmacher, 1817, non Siliqnarius, 

 alias Siliquaria, Montf., 1810). Shell, like Solecurtus, elongated, with the beaks 

 nearly central, directed backwards, pallial sinus very deep, reaching anteriorly usually 

 beyond the beaks ; two teeth in the right and two in the left valve, the posterior one 

 in the latter often obsolete, fulcrum supporting a long and strong ligament ; 

 siu'face covered with a concentrically striated, often rough olivaceous epidermis. 



These shells chiefly inhabit the mouths of rivers of the new world ; they have 

 the general character of brackish shells. The animals, so far as they have been 

 examined, have long cylindi'ical siphons united at the base. 



16. NovacuUna, Benson, 1830. Shell transversally elongated, covered with a 

 striated, more or less rough epidermis, beaks sub-anterior, regularly incurved, hinge in 

 the left valve with three diverging teeth, the middle of which is the smallest ; in the 

 right with two teeth, the anterior usually obsoletely bifid, the posterior very oblique ; 

 pallia! sinus deep, but not extending anteriorly beyond the region of the beaks ; 

 ligament strong, ftdcrum not prominent and rather short. The Novacul'mcB inhabit 

 tidal rivers of the eastern hemisphere ; they are the representants of the American 

 Tagelus, but appear to be quite distinct. The siphons of the animal are very long, 

 cylindrical, and separated from the base, the foot is, however, club-shaped. 



llafinesque appears to have applied to a worn specimen of a NovaoitUna the 

 generic name ioMCosi/Zrt. He states that the hinge has " no teeth as in Anodonta, 

 but a hinge with a marginal nerve, or fold anteriorly, distinct from the margin 

 and a little oblique behind," (see complete writings of C. S. E-afinesque on rec. 

 and foss. Conchology, by Binney and Try on, 1864, p. 84). The hinge-teeth of 

 NovacuUna, like those of Pharella, are very easily broken away, and there is often 

 no trace of them perceptible in apparently perfectly well preserved specimens. 

 NovacuUna has a distinct margin at the hinge and a slight groove extending ante- 

 riorly ; it appears therefore very probable that Ha^nosciue's Zioncosilla solenoic/es 

 was an old worn specimen of NovacuUna gangetica. 



Two such genera, as NovacuUna and Tagelus, form, not only in the arrange- 

 ment of the diverging hinge-teeth, but also through the deep pallial sinus, the long 

 and divided siphons of the animals, and their mode of living, a distinct passage to 

 Sanguinolaria, SoleteUlna, and other typical genera of the next family. 



Species of Solenid^-e from cretaceous rocks. 



Regarding' the correct generic determination of most of the cretaceous species, only a tew 

 suggestions can be made. (See Pietet and Campiehe, Pal. Suisse, 4°"' ser., 186-1., p. 29, etc.). 



1. — Solen Dupinianus, d'Orb., known only by a fragment perfectly insufficient for dcter- 

 niiiiation. 



