376 MR. R. B.WATSON ON MADEIRAN MOLLTJSKS. [Mar. 18, 



Hab. Gorgullio, shore (very rare) ; Piedade (Canigal), 15-35 

 fathoms ; Ponta de S. Lourencn, 25-45 fathoms ; Porto Santo, up to 

 50 fathoms; Santa Cruz, 10-15 fathoms; Machico, 10-15 fa- 

 thoms ; Porta da Cruz, up to 50 fathoms ; Funchal Bay, up to 50 

 fathoms. 



This species is accepted as new by Mr. Gwyn Jeffreys and by the 

 Baron Schwartz. 



From R. moniziana this species differs in that it is thinner, nar- 

 rower, more pointed, more brilliant ; the spiral threads do not pre- 

 sent the same contrast with the interstices ; these last are not so 

 broad. The mouth is rounded and on the same plane, not of the 

 strange, triangular, oblique spoon-shape it has in that other. 



It certainly resembles the smooth and small variety of R. canari- 

 ensis, in which the stain on the embryonic tip is often almost invisible; 

 except in badly rubbed specimens of that species, however, some 

 trace of that stain can be seen. Besides, this species as compared 

 with R. canariensis is always narrower in proportion to length, is 

 thinner, has the spiral threads more raised ; and even when it has 

 some trace of longitudinal ribs, these never show on the spiral 

 threads. The labial rib, too, is by comparison quite insignificant. 



From R. aurantiaca it differs in that it has fewer, higher, and more 

 distant threads, and no regular, raised, longitudinal ribs. 



A Sicilian Rissoa kindly sent me by the Marquis of Monterosato 

 is quite certainly not this species. He has published the specific 

 name above given. 



Rissoa canariensis, D'Orbigny. (Plate XXXV. fig. 12.) 



Not in M'Andrew's list. 



Hab. Gorgulho, shore; Santa Cruz, shore to 15 fathoms; 

 Machico, shore to 15 fathoms ; Piedade (Canical), 15-35 fathoms ; 

 Ponta de S. Lourengo, 25-45 fathoms ; Funchal Bay, up to 50 

 fathoms ; Porto da Cruz, up to 50 fathoms ; Porto Santo, up to 50 

 fathoms. Semifossil, Cani§al beds. Teneriffe, shore (UOrbiyny) ; 

 40-60 fathoms (M' Andrew). 



This species presents several variations of form ; but I am not 

 struck by those, specially mentioned by Signor Manzoni, dependent 

 on great differences in the proportions of the length and breadth of 

 the shell. As in all the mollusks, some are larger than others, some 

 are a little broader in proportion to length. The variety which de- 

 parts most widely from the typical form is one uniform in colour, 

 sometimes very light, sometimes dark chocolate, with the longitudinal 

 ribs reduced to mere striae and much diffused and the spiral threads 

 also much lowered ; in this form it resembles a small variety of 

 R. punctura, from which, however, it is easily distinguishable, above 

 all, by the embryonic apex. 



I cannot but think that R. philippiana, Jeffreys, is only a striking 

 and somewhat aberrant variety. It is identical with R. catiariensis 

 in the microscopic fretting of the whole surface, and especially in the 

 microscopic markings of the embryonic whorl. 



R. canariensis differs from R. spreta in having no fosse on th" 



