234 



PROCEEDINGS COTTESWOLD CLUB 



1911 



GERVILLIA RICHARDSONI sp. nov. PI. XXVII., 

 Figs. 3a and b. 



Description. — A very high subquadrate shell, with a short hinge-margin. 

 The anterior margin is slightly concave, making with the cardinal margin, an 

 apical angle of about 60°. The posterior margin is straight, but curved round 

 at its dorsal end into the cardinal margin — making with it, roughly speaking, 

 an obtuse angle. The hinge-area has about six transverse sulcations, the 

 distance between any two sulcations being equal to the width of one of them. 



Remarks. — This species is closely allied to Gervillia bathonica 

 Morris and Lycett, but differs therefrom in having a greater 

 apical angle. 



The holotype (figured on PI. XXVII., figs. 3a and b) is in 

 Mr Richardson's collection and is from the Neaeran Beds (pro- 

 bably Bed 18) of Sharp's-Hill Quarry, near Hook Norton, 

 Oxfordshire. 



PERNA OXONIENSIS sp. nov. PI. XXVII., figs, la, b, c and d. 



Description. — Shell with a subtriangular outline ; cardinal margin very 

 long, being extended posteriorly to form an acuminate posterior wing. An- 

 terior extremity pointed. The anterior margin is concave immediately below 

 the umbo, making an angle of 60° to 70° with the hinge-line ; posterior margin 

 concave. 



The shell is inaequivalve, the left valve being more convex than the 

 right especially towards the umbo. The umbo of the right valve is not 

 prominent. 



The hinge-area is wide and has five or six deep ligamentary grooves. 



Remarks. — The length of the hinge margin, the pointed 

 posterior wing, and the subtriangular form of the shell, dis- 

 tinguishes this species from Perna rugosa Miinster, P. rugosa 

 var. quadrata Morris and Lycett, and from P. mytiloides 

 Lamarck. The hinge-margin is also relatively longer than in 

 P. obliqua Lycett — the latter species being narrower anteriorly 

 and having a narrower hinge-area with more numerous sulca- 

 tions. 



The holotype (PL XXVII., figs, la, b, c, and d) is from the 

 Perna-Bed of the Bell-Inn Quarry, Enstone, and is in Mr 

 Richardson's collection. 



