MAZATLAN UNIVALVES 189 



246. DENTALIUM CORRTJGATUM, n. s. 



D. t, albido-corned, subdiaphand, parum arcuatd, gracili, 

 superjicie concentrice irregular it er corrugatd, rugulis minimis, 

 confertissimis ; aperturd brancJiiali simplici. 



One very young specimen only was found of this species, 

 remarkable for its concentrically wrinkled surface. Long. '05, 

 lat. '005 '01. 

 Hab. Mazatlan ; 1 sp. off Spondylus calcifer ; Lpool Col. 



Tablet 881 contains the specimen. 



247. DENTALIUM ? PRETIOSUM, Nutt. (teste lids.) 



Tablet 882 contains a fragment of a smooth species. It is 

 affiliated to the above, because a specimen in Mr. Darbishire's 

 collection, brought along with Lyonsia diaphana, seems to have 

 come from Mazatlan. This latter, a very small one for the 

 species, measures long. 1*56, lat. '05 '15. 



Hab. ? Mazatlan ; extremely rare, off Chama ; L'pool Col. 



ORDER SCUTIBBANCHIATA, Gray. 



Scutibranchiata + Cyclobranchiata + Pectinibranchiata (pars) 

 Cuv. 



FAMILY CHITONID^. 



Our knowledge of this most aberrant family is very incom- 

 plete. Many genera have been proposed by Dr. Gray in the 

 Proc. Zool. Soc. 1847, pp. 63, 126, and others by II. fy A. 

 Adams, Gen. vol. i. pp. 467-484 ; and others by Dr. Shuttle- 

 worth of Berne. This fullest account of their physiological 

 structure will be found in "Middendorjfs Malacozoologia 

 gia Rossica, St. Petersburg, 1847, Part I ; Beschreibung und 

 Anatomic ganz neuer oder fur Russland neuer Ckitonen ; " in 

 which 152 large 4to pages, and 14 plates are devoted to the 

 elucidation of 21 species. Additional information is given in 

 his "Seise in den Aussersten Nor den und Osten Sibiriens, 

 Part II. St. Petersburg, 1851," pp. 163-183, pi. 13-15. Most 

 of the Mazatlan species are extremely small. None of them 

 are known to inhabit any other district, except Lophyrus 

 sanguineus, about which there is still some doubt. Throughout 

 the world, they appear to be among the most local of shells. 



