OXYCHONA. XXXV11 



N. binneyanus Pfr., xi, 164. (?) N. heterogyrus Phil., xi, 174. 



N. vadum Pils., xi, 165. N. sowerbyi Rve., xi, 174. 



N. filiola Pils., xi, 165. N. arboriferus Pils.,xi, 175; xiv, 

 N. cora Orb., xi, 166. 153. 



v. unicolor Pfr., xi, 167. f. rectistrigatus Pils., xi, 176. 



N. tessellatus Shutt., xi, 167. f. latistrigatus Pils., xi, 176. 



v. atahualpa Dohrn, xi, 168. N. patasensis Pfr., xi, 176; xiv, 



v. perincrassatus Pils., xi, 169. 153. 



N. papillatus Morel., xi, 169. N. lobbi Rve., xi, 177; xiv, 153. 

 N. catamarcanus Pfr., xi, 170. v. ptychostylus Pfr., xi, 178. 



N. millegranus Mart., xi, 170. N. decussatus Rve., xi, 178; xiv, 

 N. rhodolarynx Rve., xi, 171. 154. 



devillei Hupe. v. myristicus Rve., xi, 178. 



N. platystornus Pfr., xi, 172; xiv, v. brownii Pils., xi, 179. 



153. N. ccerulescens Pfr., xi, 180. 

 N. altoperuvianus Rve., xi, 173. v. columna Pils., xi, 180. 



v. gracilior Pils., xi, 173. 



Genus OXYCHONA Morch, 1852. 



Man. Conch, xi, p. 181. Type 0. bifasciata Burrow. 



Shell trochiform, with conspicuous peripheral keel, the nepionic 

 whorls evenly latticed, as in Dryin&us. Jaw composed of many 

 vertical plaits, not converging in the middle. Radula with V-shaped 

 rows of nearly similar teeth throughout, the middle cusps very large, 

 spatulate ; ectocones wanting on the central, present on the lateral 

 teeth. Basal plates rather large and squarish (see vol. ix, p. 189, 

 pi. 51, figs. 9, 10, 11, teeth and jaw of 0. bifasciata). Genitalia 

 unknown. 



In the peculiar teeth of the radula, arranged in strongly V-shaped 

 rows, Oxychona resembles Zaplagius. But in the latter group 

 entocones are distinctly developed on all but the three inner lateral 

 teeth, and the basal-plates are narrow. Liostracus has a some- 

 what similar dentition, owing to the wide mesocones; but the rows 

 of teeth are nearly straight, and the structure of both basal-plate and 

 cusps is more like normal Drymaus. In Zaplagius the outer mar- 

 ginal teeth are distinctly less modified than the rest of the radula, 

 but in Oxychona the whole series is modified. 



Species all of eastern Brazil, and evidently arboreal. The 

 pertinence of 0. gyrina Val. to Oxychona is doubtful, as neither the 



