MAZATLAN UNIVALVES 18S 
246, DENTALIUM CORRUGATUM, 2. S. 
D. t, albido-corned, subdiaphand, parum arcuata, gracili, 
ae . ° . A . . . . 
superficie concentrice irregulariter corrugatd, rugulis minimis, 
confertissimis ; apertura branchiali simpler. 
One very young specimen only was found of this species, 
remarkable for its concentrically wrinkled surface. ong. ‘05, 
lat. *005—'O1. 
Hab.—Mazatlan ; 1 sp. off Spondylus ealcifer ; L’pool Col. 
Tablet 881 contains the specimen. 
247. DENTALIUM ? PRETIOSUM, Nutt. (teste Hds.) 
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 Jong. 1°56, lat. *05—'15. 
Hab.—? Mazatlan ; extremely rare, off Chama; L’pool Col. 
Orper SCUTIBRANCHIATA, Gray. 
Scutibranchiata + Cyclobranchiata + Pectinibranchiata (pars) 
Cw. 
Famity CHITONID i. 
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 H. & 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 “Middendorff’s Malacozoologia 
gia Rossica, St. Petersburg, 1847, Part 1; Beschreibung und 
Anatomie ganz neuer oder fiir Russland neuer Chitonen ;” in 
which 152 large 4to pages, and 14 plates are devoted to the 
elucidation of 21 species. Additional information is given in 
his “Reise in den Aussersten Norden und Osten Sibiriens, 
Part II. St. Petersburg, 1851,” pp. 163-183, pl. 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, 
