300 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



A. Adams being among the greatest sinners in these respects. The re- 

 vision of (lie nomenclature by Dr. Carpenter with the co-operation of 

 the writer w as incomplete at the time of his death, and is not yet per- 

 fected. It would he out of place here, even if ready for publication ; but 

 a few words on the genus Chiton as restricted by Carpenter may not be 

 superfluous. 



1758. — Linne" described the genus Chiton in the tenth edition of the Systcma Nature 

 according lour species to it, of which only one, C. tuberculatus, is identifiable. 



1766. — S. N. ed. xii. Nino species were described by Linne", of which the first is 

 unrecognizable and the second is C. tuberculatus. 



1776. — Muller (Prodr. Zool. Dan.) describes several species, but selects no type. 



1784.— Spengler monographs the group; his first species is C. tuberculatus L. 



1798. — Tabl. filem. p. 391, Cuvier gives an unrecognizable C. punctatus as his sole 

 example. 



1799. — Lamarck (Prodr. An. s. Vert. p. 90) gives as his sole example C. tuberculatus 

 Lin. 



1801. — Lamarck (Systeme An. s. Vert. p. 66) gives as an exanrplo C. gigas Chem- 

 nitz, not a Linnean species. 



1815-18. — Wood (Gen. Conch, and Iudex Test.) gives as his first species in both 

 cases C. tuberculatus L. These works antedate Lamarck's Hist. An. s. Vert. 



1854. — Messrs. Adams selected, as the type of Chiton, C. aculeatus Auct., an unfortu- 

 nate proceeding, since the C. aculeatus of Linne" is unrecognizable. This arrangement 

 was properly rejected by Dr. Gray and Dr. Carpenter. 



From the rules for zoological nomenclature it follows that a type can- 

 not be selected by any one for a genus proposed by any author which 

 type was not known to and included by that author in his original list 

 of species, if he himself omitted to specify a type. 



C. tuberculatus, though described from an imperfect seven- valved spe- 

 cimen, is recognized by Hanley as Chiton squamosum of Born. It is 

 figured by Eeeve as C. squamosus L. var. ,3 (Conch. Ic. pi. iv, f. 23), and 

 in the index is called "striatm Barnes." It has not been generally 

 united with the C. squamosus of L. (S. N. ed. xii), but is not improbably 

 a variety of it, and belongs to the same restricted group. It comes from 

 the West Indies. Under the circumstances, there can be no doubt that 

 it should be considered as the type of the genus, not only because it is 

 the only recognizable species of those orginally described, but because 

 it was selected by Lamarck as his sole example of the genus in 1700, and 

 served as the first species in many of the earlier works in which the 

 Chitons were enumerated or described. The genus Chiton was called 

 Lophyrus by Adams, from the name applied to the animal by Poll, who 

 was a non-binomial writer. It was more correctly treated by Gray and 

 by Dr. Carpenter in his later writings, though at one time lie had, with- 

 out investigation, followed the lead of Messrs. Adams. 



The first; authors to whom science is indebted for discriminating the 

 different groups or genera of Chitons are chiefly Guilding, Lowe, Shuttle- 

 worth, and Gray. As all the characters were not perceived at the out- 

 set, even these writers were not perfectly consistent in their grouping, 

 as has since become evident. But this was inevitable, and it only 



