1873.] 



MR. R. B. WATSON ON MADEIRAN MOLLUSKS. 



361 



Plate XXXIII. 



Fig. 1. Sithon aurea, p. 352. 



2. scopula, p. 352. 



3. pallida, p. 352. 



4. valida, p. 352. 



5. Amblypodia olinda, p. 354. 



Fig. 6. Papilio lowii, p. 358. 



7. Astictoptcrus armatus, p. 359. 



8. Plenoneura signata, p. 360. 



9. Satarupa affinis, p. 360. 



6. On some Marine Mollusca from Madeira, including a new 

 Genus of the Muricidce, a new Eulima, and the Avhole of 

 the Rissoee of the Group of Islands. By the Rev. 

 Robert Boog Watson, F.R.S.E., F.G.S * 



[Eeceived February 3, 1873.'] 

 (Plates XXXIV.-XXXVI.) 



To the 127 species named by Mr. M 'Andrew in his necessarily 

 imperfect list of Madeiran shells published in 1854 I have added 

 some 200 or 250 more, making about 400 in all. Of these, 80 or 

 90 are probably new. 



I propose to publish the rest as may be convenient. In the 

 mean time I begin with a somewhat remarkable new genus, a new 

 Eulima, and the whole of the Rissoee which I have noticed here. 



Of species already described, some present peculiarities in their 

 Madeiran forms worthy of notice. 



The measurements I offer are somewhat elaborate, but may easily 

 be passed over by those who will. I think some may find them 

 very useful. They are the average resulting from very many tire- 

 some observations. 



I reject Latin in the descriptions. That language refuses to lend 

 itself pliantly to such purposes ; and no man's ease in its use, though 

 of ready acquisition, enables him to throw individuality into his 

 word-pictures. 



Chascax, gen. nov., Watson. 



(xdaicaZ, a gaper, so called from the immense open umbilicus in its 



snout-like base.) 



Shell spindle-shaped, strongly umbilicated, longitudinally ribbed 

 and spirally ridged, but without varices. Epidermis horny. Mouth- 

 edge angulated. Outer and inner lip quite smooth. Canal long, 

 narrow, and deep, bent a little to the left, but not at all reversed in 

 front. 



Operculum strong, horny ; nucleus terminal, internally strength- 

 ened by a broad ridge all along the right margin. 



I regret to propose a new genus, believing as I do that great 

 wroug has thus been often done to true science, the reckless multi- 

 plication of genera causing a stumbling-block even more pernicious 

 than that of species-mongering. But in this case there is no help 

 for it. It is obvious that to no genus, as at present defined, can this 

 mollusk be reduced ; and both Mr. Gwyn Jeffreys and Dr. Fischer, 

 * Communicated by J. Gwyn Jeffreys, F.R.S., F.Z.S. 



