Williamson West American Mitridse. 195 



Mitra idae Melvill. 



Mitra idx Melv., Description of a New Species of Mitra, The Conchologist, 

 Vol. II, part 6, p. 140, pi. 1, fig. 6, 1893; Sowerby and Fulton's Cata 

 logues of Recent Mollusca. 



Mitra maura Swainson non Carpenter Report Brit. Asso. Ad. Sci. for 

 1856, London, 1857: Report B. A. A. S., 1863, pub. 1864; Cooper* Geo 

 graphical Cat. Moll., 1867; Tryon Man. Conch., Vol. IV, p. 121, 

 1882; Orcutt, Proc. U. S. Nat. Mus., p. 336, 1885; Cooper, Seventh An. 

 Report State (Calif.) Min., p. 251, 1887, pub. 1888 ; Keep, West Coast 

 Shells, p. 42, 1887; Bowers,f Ninth An. Report State (Calif.) Min., p. 

 58, 1889, pub. 1890; Hemphill, Cat. N. Amer. Shells, p. 2, 1890; Yates, 

 Bull. Santa Barbara Soc. Nat. Hist., p. 44, 1890; Williamson, Proc. U. S. 

 Nat. Mus., Vol. XV, p. 211, 1892 ; Kelsey, The Nautilus, Vol. XII, p. 89, 

 1892 ; Arnold, Mem. Cal. Acad. Sciences, p. 222, 1903 ; Keep, West Am. 

 Shells, p. 166, 1904; Arnold, The Tertiary and Quaternary Pectens of 

 California (P. P. No. 7, U. S. Geological Survey), p. 36, 1906 ; Williamson, 

 Some W '. American Shells, Including a New Var. of Corbula luteola,etc. 

 (Bull. S. California Acad. Sciences) p. 123, 1905. 



It is evident from the synonymy that the West Coast shell commonly 

 called Mitra maura Swains, was presumed to be like the one from Peru 

 described by Swainson (Proc. Zool. Soc. 1835). When Miss Ida Shephard 

 Mrs. Oldroyd (for whom the shell was named), sent the California 

 shell as M. maura, Mr. Fulton, on comparing it with those in the British 

 Museum from Peru, detected the difference and invited Prof. James Cosmo 

 Melvill, M. A., F. L. S., who had described something like 40 species of 

 Mitras, to describe it. The specimen was from Point Loma, California, 

 length, 2.25 in., diam. .75 inch. 



In his description Prof. Melvill says : " This interesting species belongs 

 to a section of the genus which has its headquarters on the western shores 

 of North America and Mexico, of which Mitra lens (Wood) may be taken 

 as the type, all the species possessing a black or dark-brown epidermis, 

 and being more or less decussate or puncto-striate, and it is not unlike the 

 recently described M. fultoni (E. A. Smith) from the same locality. Differ 

 entiation, however, seems easy between them." (Des. of a New Species of 

 Mitra by James Cosmo Melvill, M. A., F. L. S.) 



Specimens of Mitras from San Pedro and San Diego, that were locally 

 known as M. maura, were submitted to Professor Melvill by the writer, 

 and he unhesitatingly pronounced the larger ones the same as the type 

 specimen, in his possession, of M. idse. Young specimens of M. idse are 

 lighter brown in color and smooth, although occasionally one is found 

 which shows the lirse.J Of the shells submitted \ he wrote that they dif- 



* In Cat. W. N. Amer. and Foreign Shells, with Geog. Ranges and Labels, etc., by 

 J. G. Cooper (State Min. Bu. Spr. 1894), Mitra maura is listed as " Sowerby's " instead of 

 " Swainson's," evidently a misprint as Dr. Cooper cites the authority correctly elsewhere. 



t Mitra maura Rve. (?)" evidently a misprint. 



t Prof. F. W. Kelsey has kindly given the writer the following measurements of young 

 Mitras : " The two best young specimens I have measure 7x17 mm. Ratio 2.43. The adult 

 M. maura 21x68 mm. Ratio 3.24, and 18x58 = 3.22, while the M. fultoni are in same ratio. 

 The juv. specimens, therefore, you notice are far from same proportions as the adult, al 

 though having all the markings and coloring of (idx) maura. n 



\ See figures on page 194. 



