188 H. HICKS ON THE SUCCESSION OE 



The glabella of nearly equal width throughout, and with the 

 furrows directed forward, are distinguishing characters in this species, 

 and enable it to be easily recognized from Calymene parvifrons and 

 Calymene Murchisoni, the other species common to rocks of this age. 



Locality and Formation. Llanvirn Quarry : Upper Arenig. 



Dinobolus ? Hicksii, Davidson. PI. X. fig. 6. 



Mr. Davidson, F.P.S., to whom I submitted specimens of this 

 species for examination, believes it to be more nearly allied to 

 Dinobolus than to any other known genus; and he has therefore 

 named it as above. 



Description. — 1| inch wide by about 1J inch long. Central 

 portion moderately convex, thin and flattened out at the sides and 

 towards the anterior margin; flattened also towards the umbo, 

 which is but very slightly produced. Surface marked with tolerably 

 well-defined lines of growth. 



This species, according to Mr. Davidson, approaches nearest in 

 shape to Dinobolus transversus, Salter ; but as it is from much earlier 

 rocks than that species, it is probably distinct. It also gives the 

 genus a much lower range than has hitherto been ascribed to it, 

 and is interesting therefore as being the earliest known species. It 

 is unfortunate that the material is not perfect enough for giving a 

 proper diagnosis ; but it is to be hoped, now that the beds in which 

 it was found are under examination, that better specimens will 

 soon be found. 



Locality and Formation. Llanvirn Quarry : Upper Arenig. 



OrHILETA, sp. PL XI. fig. 3. 



This is much like the specimen figured by Mr. Salter in Mem. 

 Geolog. Survey, 1866, pi. 11 b. fig. 21 ; but it is too imperfect to 

 describe or to give it a specific name. Mr. Salter's species was 

 found in the White-Grit Mine, Shelve, and hence in beds probably of 

 the same age as the Llanvirn beds, in which I found this specimen. 



Locality and Formation. Llanvirn Quarry : Upper Arenig. 



Pleueotomakia llanvernensis, n. sp. PI. XI. fig. 4. 



Description. — Shell moderately convex, of five or six whorls, dia- 

 meter about y 6 ^ of an inch. Surface of the whorls smooth, nearly 

 flat, and forming a gentle slope from the tolerably acute apex to the 

 margin. On the outer edges of the whorls there is a narrow 

 slightly raised band. This is the earliest species of the genus known 

 in this country. 



Locality and Formation. Llanvirn Quarry : Upper Arenig. 



Bellerophon llanvienensis, n. sp. PI. XL figs. 1, 2. 



Description. — Spire of three very rapidly increasing whorls. Outer 

 whorl greatly expanded, but compressed. Lines of growth strongly 

 marked, arched backwards, and approximating to each other more 

 closely in the expanded outer portion. Diameter 1J inch. 



