152 SUPPLEMENT TO THE 



median ribs on the fold, but differs from the two species above named by having a larger 

 number of smaller ribs on the lateral portions of its valves. In occurs in the Llandovery 

 or May-Hill Sandstone. 



37. Rhynchonella Dayi, Dav. Sil. Sup,, PI. X, figs. 2, 2 a 5. 



Rhynchonella dayi, Dav. The Geol. Mag., New Ser., vol. viii, p. I.tI, pi. v, fig. 9, 



1881. 



Obtusely deltoid or sub-pentagonal, wider than long ; valves moderately convex, and 

 divided into three almost equal lobes. Ventral valve not quite as deep as the dorsal one, 

 divided by a broad, well-defined, mesial sinus ; beak small, showing a small, circular 

 foramen margined by a deltidium ; surface of valves ornamented with some fourteen or 

 sixteen angular ribs, of which four form a well-defined mesial fold, the ribs being slightly 

 bent upwards at the front ; lateral margins of fold wide and flat. 

 Length 5|, width 6, depth 3| lines. 



Ol>s. — This small species is well distinguished from young specimens of l^/i. horealis 

 of the same age, with which it has been sometimes confounded, by its less triangular 

 shape, as well as by the ribs of its fold being bent upwards close to the frontal extremity. 

 In size and in number of ribs, Bh. Dayi somewhat resembles small examples of the 

 Jurassic Bh. tetraedra. 



This small species was found by Mr. George Maw in the Wenlock Limestone of 

 Benthall Edge, as well as in the Wenlock Shales underlying the limestone. I have had 

 much pleasure in naming it after the Rev. H. Day. 



38. Rhynchonella cuneata, Dalman and Hisinger. Dav., Sil. Mon., PI. XXI, figs. 



7_11 . Sil. Sup., PI. X, 

 figs. 9, 9 a, 10, 10 «. 



Since describing this species at p. 164 of my ' Silurian Monograph,' Prof. James Hall 

 has, at p. 166 of the ' Twenty-eighth Annual Report of the New York State IMuseum of 

 Natural History' (1879), proposed a new genus, Rhynchotreta, for the reception of 

 Dalman's species. Prof. Hall characterises his new genus as follows : — '^ Shell triangular, 

 surface Avith angular plications. Ventral beak straight, produced beyond the dorsal beak, 

 extremity perforate, the foramen with an elevated margin ; space between the foramen and 

 hinge-line occupied by a deltidium in two pieces, being divided by a longitudinal suture, 



