CAMBRO-SILURIAN FOSSILS. 227 



opening at the apex of the beak ; interior of entering valve 

 with two very short diverging cardinal teeth, and a minute 

 rostral tooth. Width 11 lines, proportional length y^^, length 

 of disk in receiving valve -^j^q, length of disk in entering 

 valve 3%V depth j'^f^. 



This so exactly resembles some of the small varieties of L. del- 

 toidea and the L. camerata (Conrad) as figured by Hall, that I 

 should not have thought of separating them, were it not for the 

 very much finer strise, which very easily separate the species 

 from our British specimens of L. deltoidea. The foramen of the 

 apex of the beak is also larger, the dental lamellae more diver- 

 gent, and the muscular impressions much wider. I find the 

 peculiar hoof-like form and other characters of this little shell 

 (unlike L. deltoidea) to be extremely constant. 



Gregarious, in extraordinary abundance, completely filling 

 some beds of the limestone of Llansaintffraid, Glyn Ceiriog S. of 

 Llangollen, Denbighshire; limestone of Selattyn Road S. of 

 Llangollen, N. Wales. 



{Col. University of Cambridge.) 



Lingula Davisii (M'Coy) . 



Sp. Char. Ovato-pentagonal, or broadly subtrigonal, depressed, 

 slightly and broadly convex near the beak, and about half- 

 way to the margins, which become gradually flattened ; 

 greatest width at about the middle of the length ; front slightly 

 narrowed but very wide, subtruncate, and very slightly con- 

 vex, obtusely rounded at the lateral angles to the subparallel 

 slightly convex sides ; posterior lateral margins rather long, 

 forming an obtuse angle at the sides (usually nearly equalling 

 half the length of the shell, nearly straight, and meeting at 

 the beak at an angle of about 100° in the short and 95° in 

 the long valve) ; surface with numerous, faint, concentric, 

 rather wide subangular undulations of growth, accompanied 

 by irregular concentric imbricating laminar strise, ten in one 

 line on the exterior of the shell ; no trace of longitudinal ex- 

 ternal strise, but on the internal cast a few faint obsolete flat- 

 tened fibrous radiations observable with the lens. Length 7 

 lines, proportional width y'^''^, depth about ^-^q. 



This curiously wide satchel -shaped Lingula is the species dis- 

 covered by Mr. Davis in such profusion in the Lingula slates 

 near Tremadoc in company with the large elongate L. ovata 

 (M^Coy), and I have great pleasure in dedicating the species to 

 him ; at the same time I must remark, that except for a slightly 

 greater width and perhaps less coarsely undulated surface, it 

 seems scarcely to differ from the L. lata of Pander ; as however 



p2 



