268 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



was suggested by Hollard, merely as exaggerations of the crests aud 

 ridges wliicli define the lateral, dorsal, aud veutral surfaces of the cara- 

 pace, occurriug iu those parts of the body aud iu that part of the above 

 series where these crests and ridges are most emphasized, and their ab- 

 sence coiuciding with the absence of prominent lines of demarcation. 

 They are most numerous iu the middle portion of the above series, in 

 the forms transitional between the triagonal and tetragonal sections of 

 the genus, aud are alike also at both extremes. 



The geographical distribution of the species is interesting in the light 

 of this gradation. The triagonal forms (I and II) occur only in the West 

 Indies. The next iu order (III) occur not only iu the West Indies but 

 in the southeastern Atlantic. The subtriagonal form (IV) is represented 

 iu the southeastern Atlantic (at the Cape of Good Hope), in the west- 

 ern Pacific (China), in Australia and the East Indian Archipelago. The 

 subtetragonal forms (V) are represented in the ludian Ocean, west to 

 the Cape of Good Hope, in Japan and Australia, and iu the East Indian 

 Archipelago, while the tetragonal forms (VI, VII, and VIII) almost ex- 

 clusively in the Indian Archipelago and the Indian Ocean. 



There is no dearth of names for the sections of this group, but as has 

 been remarked, it is impossible to assign them or subdivide the genus 

 by any but arbitrary methods. 



Swainson's Ostracion corresponds to Divisious VI, VII, and VIII; 

 his Tetrosomus to Divisions IV and V, although he assigns 0. cornutus 

 to the following genus ; his Lactophrys to Divisions II and HI, and his 

 Rliinesomus to Division I. 



Kaup's Ostracion would include Divisions I, II, HI, and IV ; his Lae- 

 toplirys^ Division V; and his Cibotion, Divisious VI, VII, and VIII. 

 Bleeker's Ostracion includes I, VI, VII, aud VIII; his Tetrosomus, IV; 

 his Acanthostracion, II, HI, and V. 



Dr. Bleeker by assuming Di\dsiou V, instead of Division I, as one ex- 

 treme of the series, made his division of the group into subgenera more 

 plausible. This arrangement does not, however, allow as complete a 

 gradation of form. 



Suborder OSTRACODERMI/ Gill. 



Synonym as family name. 



< Sclerodermes, Cu\aER, E^gne Animal. Ist ed. ii, 1817, p. 153 ; 2d. ed. ii, 1829, p. 375. 



< Sclerodermi, Gunther, Cat. Fisli. Brit. Mus. vili, 1870, p. 207. (Synonym as sub- 



ordinal name.) 

 \ Sclerodermes, Hollaed, Ann. Sci. Nat. (4) xiii, I860, p. 31. 



Synonyms as ordinal names. 



<^ Sclerodermi, Bonaparte, Giorn. Accad. di Scienze, lii, 1832 (Saggio Distrib. Metod. 

 Animali Vertebr. a Sangue Freddo, p. 39). 



* The synonymy of this suborder is in substance quoted from Gill. MS. 



