MAZATLAX ITKIVALTES 189 



246. DENTALItJil COEEtTGATUM, n. S. 



D. t. albklo-corned, suhcVmphana, panim arcuata, gracili, 

 superjicie concentrice irregulariter corrugata, rugulis minimis, 

 confertissimis ; apertura hrancJiiali simplici. 



One very young specimen only was fonnd of tliis species, 

 remarkable for its concentrically wi-inkled surface. Long. '05, 

 lat. -005— -01. 



Hah. — Mazatlan ; 1 sp, off Spondylus calcifer ; L'pool Col. 



Tablet 881 contains the specimen. 



247. Dentalium ? PEETiostrM, Nutt. (teste Hds.) 



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

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



Hub. — ? Mazatlan; extremely rare, oflf Chama ; L'pool Col. 



Oedee SCUTIBEAJS'CHIATA, arm/. 



Scutibranchiata + Cj'clobranchiata + Pectinibranchiata (pars) 

 Cuv. 



Family CHITONID.E. 



Our knowledge of this most aberrant family is verj- incom- 

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

 Proc. Zool. Soc. 1847, pp. 63, 126, and others by S. ^' A. 

 Aiams, Gen. vol. i. pp. 4^7-484 ; and others by Dr. Shuttle- 

 worth of Berne. This fullest account of their physiological 

 structure wiU be found in "Middendorjfs 3Ialacozoologia 

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

 Anatomic ganz ne^ier oder fiir Sussland neuer Chitonen ;" in 

 which 1.52 large 4to pages, and 14 plates are devoted to the 

 elucidation of 21 species. Additional information is given in 

 his "Seise in den Ausserstcn Nordcn und Osten Sihinens, 

 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 anj^ 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. 



