92 POLYPLACOPHORA. 



A. TESTUDO Spengler. This name is proposed by Spengler for the 

 Red Sea form, which I have treated in vol. xiv, p. 222 as a variety 

 of J., spiniger. This name cannot be adopted in preference to the 

 specific name spiniger, because Spengler gave no description what- 

 ever. See Skrivter af Naturhistorie-Selskabet, iv, p. 78, and Mai. 

 Bl. xvii, p. Ill, 112. The " Ch. aculeatus" of Spengler is A. 

 spiniger. Rochebrune's name balansce was applied to the Red Sea 

 Acanthopleura, but it has not been acceptably defined. 



Family A CANTHOCHITID^ (Vol. XV, p. 6). 



Genus ACANTHOCHITES Risso. 



Add to generic synonyms: Mecynoplax Thiele, Das Gebiss der 

 Schnecken ii, p. 393, for acxdirostratus Rve. [?] from Hakodate ! 



Genus AMICULA Gray, {Antea, p. 42). 



Add to synonyms: Stimpsoniella Cpr., Bull, Essex. Inst. 1873, 

 p. 155 ; Ann. Mag. Nat. Hist. (5) xiii, p. 122, 1874. 



APPENDIX II. 



Insufficiently described Chitons, and species of unknown 



GENERIC position. 



In a group so prolific in specific and varietal forms as the Chitons, 

 we expect to find a certain number of descriptions of supposed new 

 forms so inadequate that their recognition is extremely difficult or 

 impossible. In most grouj^s we find that the earlier authors, not 

 appreciating the niceties of modern species discrimination, having 

 but a few out of the multitude of specific forms, and being without 

 precise technical language, have contributed the greater part of such 

 literature. In the Polyplacophora the bulk of this descriptive matter 

 has been a recent growth, and is in large part due to the labors of 

 Dr. A. T. de Rochebruue, Aid Naturalist at the Paris Museum 

 (Jardin des Plantes). The various memoirs by Rochebrune describe 

 a multitude of supposed new forms, but so incompletely that only in 

 rare instances can they be recognized, and even the genus can 

 scarcely ever be ascertained from his descriptions. In his use of the 

 generic terms of Gray and others he has been most unfortunate, 

 employing them correctly in but few cases. After much study I 

 have ascertained the fundamental principles of Dr. Rochebrune's 

 classification of Chitons to be as follows : 



