4 



BRITISH FOSSILS. 



specimens exhibit the dimensions of No. 3. Of the six, Nos. 1, 2, and 4 

 may be regarded as belonging to form /3, No. 3 to form cc, the most 

 common variety, No. 5 to var. y, and No. 6 to var. ^. These different 

 forms have really scarcely any claim to the rank of varieties, for every 

 degree of intermediate shape is exhibited by specimens collected in the 

 same localities. 





1 



2 



3 



4 



5 



6 





Length . 



1 



^ 12 



0 Ji 



" 12 



Oil 



Oil 





Breadth . 





o!i 



Oil 



Oil 



0 \t 



0 \i 





Height . « . 



Oil 



0 7, 



Oil 



Oil 



^ 12 



Oil 





British Localities and Geological Range. — Upper green sand — 

 Warminster, Wiltshire (Survey Collections) ; Chute Farm, Wiltshire ; 

 Hythe, Kent (Morris). Junction beds of upper green sand and chalk 

 MARL, Maiden Bradley, Wiltshire (Bristow), (Survey Collections). 



Foreign Distribution. — Upper green sand of France and Germany. 

 C. columbarius, as defined by D'Archiac, is from the Gault of Mans, 

 Coulaines, and Fouras. 



Description of the Plate, 



Fig. 1. Specimen of typical form seen from above. Fig. 2. Lateral view. Fig. 3. 

 Posterior view. Fig. 4. Diagram of a specimen of form jS, seen from above. Fig. 5. From 

 beneath. Fig. 6. Posterior view. Fig. 7. Diagram of relative positions of ovarian and 

 ocular pores, and summits of the ambulacra- Fig. 8. Arrangement of pores iu each 

 ambulacral series. 



April, 1849. 



E. Forbes. 



