PAPUINA. 137 



laria TAP. CAN. Ann. Mus. Civ. Genov. xix, p. 115, 138, type H- 

 lituiis, 1883. Pileolus LESSON, Voy. de la Coquille. Zool. ii, p. 

 313 (preoc.). Cymotropis v. Mart., Die Hel., p. 169, type H. 

 "vitrea" - antrorsa. Merope ALB., Die Hel., 2d edit., p. 158, 

 type H.f ring ilia (preoc.). Geotrochus of BECK and authors, not of 

 v. Has?elt. Acavus SMITH and TAP. CAN., not of Montf. 



Shell turbinate, lens-shaped or trochiform, umbilicated or imper- 

 forate, rather thin ; periphery varying from round to acutely keeled. 

 Surface smoothish, the coloring light or bright. Aperture oblique, 

 toothless or with a columellar nodule, the peristome thin and gen- 

 erally expanded, ends of the lip remote. Type P. lituus Less. pi. 

 29, fig. 12 (see also pi. 29, figs. 14, 15, P. trobriandensis. Fig. 11, 

 P. splendescens. Fig. 13, P. nortoni. PI. 46, figs. 17-19, P. ianthe). 



Animal with the foot rather short, sole undivided ; upper surface 

 densely granulated, with a slight median longitudinal groove above, 

 the tail densely granulose with no median groove. Mantle with a 

 triangular right lappet and an elongated low left one, the latter 

 emitting a lobe on the left side. 



Jaw thin and iveak, arcuate, it* median portion ribbed, ends blunt 

 and ribless. (PI. 34, fig. 11, P. moseleyi. PI. 34, fig. 12, P. vexillaris. 

 PL 37, fig. 2, P. conscendens. PI. 13, fig. 17, P. grata. PI. 13, fig. 

 18, P. taumantias. PI. 13, fig. 25, P. louisiademis. PI. 13, fig. 24, 

 P. boyeri. PI. 13, fig. 26, P. brumeriensis. PI. 13, fig. 28, P. 

 macgillivrayi. 



Radula of two types. Typically, the transverse rows are nearly 

 straight ; the central and lateral teeth with wide, blunt mesocones, 

 shorter than the basal plates, the marginals with three short, wide 

 cusps (pi. 13, fig. 23, boyeri, PI. 13, fig. 29, frinailla. PI. 37, fig. 

 11, conscenden.^. In P. moseleyi (pi. 37, fig. 1) the cusps are very 

 broad, and project beyond the basal plates. 



In some divergent species the transverse roivs of teeth are V-shaped; 

 -central teeth (pi. 37, fig. 9), with an extremely broad, gouge-like 

 cusp (united meso- and ectocones), the laterals having the cusp par- 

 tially divided into entocone and mesocone, an ectocone appearing 

 on the outer laterals and marginals. The teeth are all of the same 

 general form, and in all the cusps project over the basal plates. 

 This type of teeth occurs in P. boivini and in vexillaris (pi. 37, figs. 

 9, 10), and will probably prove characteristic of the groups those 

 species belong to, and also of the P. meta group; the other groups 

 having the more normal type of teeth. This aberrant type is com- 



