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NOTE ON TRIVIA COSTISPUNCTATA Gaskoin. 



By J. COSMO MELVILL, M.A., F.L.S. 



(Read before the Society, May 12th, 1909). 



In a recent number of the "Nautilus" (xxii., p. 126), Dr. W. H. Dall 

 reviews Senor J. G. Hidalgo's "Monografia de las Especies Vivientes 

 del Genero Cyprcsa^'' so far, at least, as the North American species 

 inhabiting, or said to inhabit, the AVestern Pacific coast are concerned. 



He observes that " Trivia costispunctata Gaskoin, 1870, reported 

 "from California, if correctly located, is probably only a mutation of 

 " T. radians Lamk." 



I conjecture that Dr. Dall has not seen the species, and as the 

 type, originally in the Gaskoin collection, has been for many years 

 in my possession, I should like to state that, in my humble opinion, 

 it is a good species, not, indeed, so near T. radians as are T. solandri 

 and the rarer and somewhat obscure depauperata Sowb. This last, 

 of which I possess a co-type from the Prevost Collection, may, 

 indeed, be a variety of radians, though much more material is required 

 for examination before this is proved. Roberts, in Tryon, Man. Conch., 

 v., p. 203, considers it a variety of californica (more correctly, as 

 pointed out by Dall, californiana Gray), but it seems nearer either 

 to solandri or radians. 



T. costispunctata Gaskoin, however, is not so rudely constructed a 

 shell as radians, nor so flattened and expanded basally. It is of a 

 pale cinereous fawn colour, rounded at the base, the ribs closer and 

 finer than in most of its allies ; nor are they so " bulbous " at the 

 dorsal sinus. It is true that some specimens of radians are occasion- 

 ally lentiginous, but the mottling of the ribs in T. costispunctata is far 

 more uniform and neat. I have seen, altogether, tln-ee or four 

 examples of this species, but it is, as is depauperata, very uncommon 

 in collections, and I imagine the locality of both is doubtful, prob- 

 ably occurring off the coast of Central America. 



Another species which T. costispunctata might by some be made 

 comparable with is the abundant Antillean T. pediculus L., and its 

 variations are considerable. Such a specimen as is figured by Sowerby 

 (Thes. Conch., xxxiv., p. 429), which shews slight lentiginous flecking 

 of the dorsal ribs, for instance, might be considered akin, but, in my 

 opinion, it is but a superficial resemblance. T. costispunctata is fairly 

 well figured, though the coloration is not good (Thes. Conch., xxxv., 

 pp. 452, 453), the drawings being taken from the type specimen 

 exhibited on the present occasion. These figures have been copied 

 in Man. Conch. Cyprcea, pi. xxii., figs. 7, 8. 



