56 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Gilchrist' so closely that T should have unhesitatingly placed it in 

 that genus, had it not differed slightly from it in the leading feature 

 upon which the genus was founded, namely, the position of the 

 rhinophores with regard to the parapodia. In Paraphjaia the rhino- 

 phores lie actually between the anterior ends of the parapodia, whilst 

 in this specimen they are 3 mm. in advance of them. On this account 

 alone it must, I think, be placed in the genus Tethys, and having 

 regard to its general similarity in other characters to the genus 

 Paraphjsia, it becomes a question, as suspected by Gilchrist himself,^ 

 whether in reality any hard and fast line can be drawn between the 

 genera Tethys and Paraplysia. 



Tethys nigrocincta (Martens). 



Of this species there was one specimen from Scottsburg, Natal. 

 It is larger than the type desciibed by Martens, and also differs from 

 it in being of a pale yellow colour instead of light brown. 



The specimen had the following measurements : total length, 28 mm. ; 

 height, (through the visceral sac) 13 mm., (in front of the parapodia) 

 6 mm. ; distance from the mouth to the anterior limit of the parapodia, 

 10 mm., the rhinophores being situated midway between these two 

 points. The parapodia are united behind to a depth of 2 mm., 

 and are separated in front by a distance of 6 mm. Their greatest 

 height is 6 mm. 



The general form of the body is long and slender, with the visceral 

 sac strongly humped up. The rhinophores and tentacles are slender 

 and ear-like. The sole of the foot is narrow (5 mm.) and very clearly 

 defined. The mantle orifice is peculiarly large (7 by 6 mm.) and 

 somewhat egg-shaped, with the narrower end directed backwards. 

 The siphon is short and wide. 



The genital opening lies in front of the anterior edge of the mantle, 

 some 2 mm. in advance of the gill. The opaline gland opens by 

 numerous minute pores. 



The colour of the animal is a delicate fulvous yellow, with very 

 faint indications of small lighter spots upon the outer surface of the 

 parapodia and down the centre of the back. The edges of the 

 parapodia, of the mantle orifice, and of the siphon are bordered by 

 an interrupted delicate black line. Black pigment also occurs within 

 the cavities of the rhinophores and tentacles, and upon the anterior 

 and posterior margins of the foot. The eyes, which are plainly 

 visible, lie just in front of the rhinophores. 



The shell : The calcareous part of the shell was unfortunately 

 broken. The uninjured beak and the periostracal layer, however, 

 give the following particulars: length, 10mm.; breadth, 8mm.; 

 height, 3 mm. The beak is strongly iuturned, and is not reflexeil. 

 The sinus is slightly concave, and occupies a little more than the 

 posterior third. 



^ Gilchrist, "The genus Paraphjsia, with description of a new species": Trans. 



S. Af. Phil. Soc, vol. xi (1902), p. 121. 

 2 Gilchrist: loc. cit., p. 124. 



