268 



ON THE EXTERNAL CHARACTERS OF SINUM PLANULATUM 



(Recl.). 



By G. C. RoBSON, F.Z.S. 



(Published by permission of the Trustees of the British Mioseum.) 

 Read 13th April, 1923. 



In the autumn of last year I received from Dr. J. D. F. Gilclirist 

 a complete specimen of Sinum planulatum (Reel.), obtained during 

 the Marine Biological Survey made by the Union Government of 

 South Africa in 1921. It was caught in 59 fathoms in Lat. 32° 11' S., 

 Long. 18° 9' E., and had been well preserved in formalin, so that the 

 colour was still fairly vivid. As the description of the external parts 

 of representatives of this interesting genus is still deficient the 

 following notes may be of service. 



/> 



W 



Sinum planulatum (Eecl.), slightly enlarged. 

 m, metapodium. 



p, propodium ; s, shell ; 



The modification of the foot in the Naticidse is a well-known 

 phenomenon, and has been repeatedly figured in textbooks. A 

 general account of Sinum planulatum has been given by Bergh ^ ; 

 but no detailed description of the external parts has been as yet 

 published in the case of this species, which probably shows the 

 maximum development of the propodium and metapodium seen in 

 this family. 



The specimen is somewhat bent on itself and cannot easily be 

 flattened out. It measures about 87 mm. in length ; a figure which 

 is twice as large as that given for Bergh's specimen. The only other 

 complete example in the British Museum measures 85 mm. To this 

 total length the propodium and metapodium each contribute the 

 same, viz. about 40 mm. The whole animal is long, narrow, and flat, 

 and only a small portion of the shell is seen projecting between the 



1 Trans. S. African Phil. Soc. xvii, 1908, p. 108. 



