348 MAZATLAN UNIVALVES 



Jf 397. LlTOBINA ASPERA, Phil. 



Proc. Zool. Soc. 1845, p. 139: AlUU. pt. ii. pi. 4, f. 13. 

 Mice, in Zeit. /. Hal. 1847, p. 178, no. 2 : do. 1850, p. 163, 

 no. 8. C. B. Ad. Pan. Shells, p. 170, no. 232.??Midd. Mai. 

 Eos. pt. ii. p. 66, no. 10. 

 Melaraphe aspera, H. $f A. Ad. Gen. 314. 



Besides the natural doubt that an essentially tropical shell 

 extremely common at Panama, less so at Mazatlan, and not 

 found at all on the Californian coast by the accurate observer, 

 Mr. JNuttall, (where it is replaced by L. planaxis,) should 

 reappear in the Boreal region of Sitcha, the description of 

 Middendorff by no means accords with Philippi's shell. The 

 Russian shell is "crassa, lineis nigricantibus obliquis picta, anfr. 

 parum convexis," and is said to resemble L. ziczac andL. zebra. 

 The evidence therefore appears to be very unsatisfactory, on 

 which Prof. Forbes, in his Zoological Map, gives this species 

 as characteristic of the Oregon fauna. A very different shell 

 from Pernarnbuco (J. P. G. Smith) is also given in the B. M. 

 as the L. aspera, Phil. 



The Mazatlan shell is (for the genus) rather thin, and toler- 

 ably constant in characters. It is readily known when fresh 

 from L. conspersa by the dark hue and sharp, distant ribs. In 

 shape it goes through the same changes as its congener ; but 

 in sculpture and colour is much more constant. The ribs are 

 sharp, with very broad concave interstices, are somewhat rough- 

 ened by lines of growth, and are beautifully tinted, in ill-defined 

 spots, with umber. The young shell (as Mke. states) has a 

 chalcedonic apex like that of L. conspersa, below which it haa 

 generally a slate coloured band. The spots also are more de- 

 fined, and run into lines. They were provisionally distinguish- 

 ed by Mke. as L. apicina. At this period the ribs are closer 

 and flattened, but still much more conspicuous than the cor- 

 responding stage of L. Philippii. The apex is commonly eroded 

 in the adult. The colour within resembles that of L. conspersa, 

 but is generally darker. The base of the young shell also 

 agrees in being often keeled or angulated. The* operculum is 

 rather broader than in that species, with the thin trasparent 

 edge less defined. Inside the nucleus is raised, and is rarely 

 seen to display the spiral elements. The muscular scar is not 

 furnished with spiral striae, but is irregularly roughened with 

 minute knobs and striae of growth. An unusually compact 

 specimen measures long. '7, long. spir. '34, lat. '5, div. 70. 

 An elongated sp, *64, '32, '4, 50. 



