Prof. F. M'Coy on some new Silurian Mollusca. 47 



Bellerophon subdecussatus (M'Coy). 

 Sv Char. Globose, of one and a half or two very rapidly en- 

 \vZ^ whorls, ubcompressed towards the very obtusely an- 

 lukr 01 rounded eircLference ; sides gibbous; umbdicus 

 S, deep, partially exposmg the whor s ; ^^^1 '' 

 in pi^portion to diameter, width -f-J^, ength of mouth -,^^, 

 IZL of umbihcus ,Vn; surface with « -Jg^ ^-ns^e^^e 

 ridges arching backward from the umbilicus to the undehned 

 band formini a wide V-shaped sinus; about four or five of 

 these transveSe ridges m the space of 1 line -ar die m^^^^^^^ 

 thev are crossed by much finer spiral stri^, about the san^e 

 dSnce apart, from one to three of which are usually stronger 

 than the rest near the band. 



This species is extremely like the carboniferous B. decussatus 

 (Flem.), but has the transverse strise much stronger than the 



'^ Rarer'the schists of Llanrwst and fine Caradoc sandstone of 

 Mulock, Dalquorhan, Ayrshire. 

 [Col University of Cambridge.) 



Holopella (M'Coy), n. g. 

 Gen. Char. Shell spiral, elongate slender of numeiws gra- 

 dually increasing whorls, generally crossed by slightly arched 

 stri^ ■ mouth circular, with the peritreme entire ; base rounded, 

 with or without a minute umbihcus. 



These shells have hitherto been confounded with the recent 

 ^enus Turritella, from which they differ completely m the entire 

 peritreme and definite round margin to the mouth, thus approach- 

 ing much nearer to Scalaria. From Chemmtziat\^Y^ diff-er in 

 the smaller size of the body-whorl, and m neither it nor the 

 mouth being produced anteally. 



Holopella gracilior (M'Coy). 

 8r) Char. Very slender, spiral angle 15°, whorls smooth (num- 

 ber unknown), slightly and evenly convex, suture deep, simple 

 sutural angle 95° ; width at base 5 Imes, length of last whorl 

 3 lines. 



This is distinguished from the/f. ohsoleta by its more slender 

 spire (as indicated by the difference in their spiral angles), less 

 convex whorls, &c. 



Schists of Dinas Bran, Llangollen. 

 {Col University of Cambridge.) 



Holopella intermedia (M'Coy). 

 I provisionally give this name to a species agreeing exactly. 



