R. Bullen Newton — Marine Fossils from Mekrcin Coast. 299 



shell structure on the postero-ventral region, which well illustrates 

 the smooth, narrow-banded character of the sculpture. I have net 

 been successful in discovering a shell which is suitable for com- 

 parison with this species, either among modern or fossil forms, its 

 chief characters having reference to the triangularly oval shape and 

 the regular concentric banding which ornaments the valve. 

 Example. — One specimen only in the collection. 



Cakdium Melvilli, n.sp. (PI. XVI, Figs. 1-4.) 

 Shell globose, nearly equilateral, radiately costated ; costee about 

 37, depressed, angulated at the sides, separated by narrow, deep 

 interspaces about one-half the width of the ribs (as seen near the 

 ventral margin) ; umbones rounded, incurved, subcentral. 



Dimensions. — Umbono-ventral 



Antero-posterior 



Diameter (closed valves) 



This is one of the most abundant shells found in the Mekran 

 nodules, though always occurring as internal casts. Some original 

 costal structure still remains on the ventral area of the lai'ger 

 specimen selected for illustration, showing that the ribs have rather 

 wide flattened summits covered with delicately vaulted surface 

 lineations, angulated sides, and divided by narrow sulcations which 

 are closely and concavely striated within. In its well-arched and 

 globular form and the great number of its ribs this species resembles 

 C. asiaticum of Bruguiere and G. multispinosiim of Eeeve, both living 

 Pacific shells, though differing in the structural details of the costae. 

 In C. asiaticum the costffi are more elevated and narrower, besides 

 being sharply lamelliform on the posterior region of the valves ; 

 and instead of lineations the surface exhibits a minutely granulate 

 structure. The ribs in C. midtispinosiim are more rounded, besides 

 being numerously spined with small projections. I know of no 

 Miocene or Pliocene shell which suggests affinities with this species. 



The species is named after Mr. J. Cosmo Melvill, M.A., F.L.S., who 

 is one of our principal authorities on the modern conchology of tlie 

 Persian Gulf. 



Examples. — Numerously represented in the collection. 



DosiNiA sp. (PL XVI, Figs. 8-10.) 

 This shell is represented by a fractured left valve which exhibits 

 both internal and external characters, the former including parts of 

 the anterior and posterior surfaces, with complete margins, and 

 giving good views of the adductor scar markings; through the 

 broken surface of the centre of the valve the typical concentric 

 lineations of this genus are well exposed. The other half of the 

 nodule contains a natural cast of the valve showing impressions 

 of the muscular markings and the pallial line with its conspicuously 

 lanceolate, triangular sinus. 



It is not possible to say more in connection with the specimen 

 than that it somewhat resembles the European species D. exoleta, 

 which is similarly orbicular, besides agreeing in general dimensions j 



