XXXVill ZAPLAGIUS. 



apical sculpture or tlie dentition is -known. It probably groups with 



B. pileiformis Moric. 



O. bifasciata Burr., v, 129; xi, O. lonjhostoma Mke., v. 130. 



181. ?O. gyrina Val., v, 131. 



v. mimarum Anc., xiv, 154. 



Genus ZAPLAGIUS Pilsbry, 1896. 



Nautilus ix, p. 115, Feb., 1896; Man. Conch, xi, 185. Type 

 Helix navicula Wagn. Navicula Spix, 1827, not of Blainville, 

 1825 Otostomus of some authors. 



Shell conic or obliquely conic, with the apical sculpture of typical 

 Drymaus, and a keel around the truncate or flattened base ; the last 

 whorl ascending, lip expanded or reflexed, thin. 



Jaw deeply arched, with narrow plaits (43 in aurisleporis) con- 

 verging mesially as in Drymceus. 



Two widely separated lobes are on the left edge of the mantle. 

 The kidney is the length of the pericardium (Semper). 



The genital system (pi. 50, h'g. 8, Z. aurisleporis, after Semper) is 

 simple, the long slender penis having a terminal retractor, and the 

 ovate spermatheca a long duct, as in Bulinmlus, J)rymdeus, etc. 



The radula (of Z. aurisleporis, pi. 58, figs. 70-7 4, from a specimen 

 supplied by Dr. H. v. Ihering) has 37.1.37 teeth in V-shaped rows 

 (pi. 58, fig. 74). The median tooth of each row has an exceedingly 

 large, rounded cusp, the basal-plate being narrow except under the 

 cusp. The lateral teeth have similar but subangular cusps, more or 

 less emarginate near the inner side, indicating the concrescence of 

 an entocone with the mesocone; and far back there is a minute, 

 vestigeal outer cusp, remote from the main cusp, as in some 

 Urocoptidse. The fourth to sixth laterals show the entocone as a 

 short prong, becoming stronger as we pass outward on the radula 

 (fig. 70, llth and 12th, and fig. 71, 21st and 22d teeth). The mar- 

 ginal teeth (pi. 58, fig. 73, 33d to 37th teeth) have a large mesocone, 

 a retreating and distinct entocone, and the ectocone has traveled for- 

 ward, become larger and usually bifid. They thus approximate to 

 the marginals of typical DrymcKus. 



With the apical sculpture, jaw, and general anatomy of Drymseus, 

 this group seems sufficiently specialized in dentition and shell to 

 stand as a distinct genus. Its close relationship to Oxychona can 

 hardly be doubted. The eastern Brazilian Otostomus signatus may 

 also be related, but its soft anatomy is unknown. 



