174 PARTULA, MARQUESAS ISLANDS. 



on the upper half of the last whorl. The type specimen (no 

 4264 Carnegie Mus.) is not completely mature, wanting the 

 narrow callous inner rim of the peristome, but there are 

 several fully adult shells with younger ones in the collection 

 of the Academy, taken by C. D. Voy. An egg shaken from 

 one of them is very shortly oval, 3 x 2.5 mm., matt white, and 

 smooth under an ordinary lens. 



5. P. DECUSSATULA (Pfeiffer). PI. 31, figs. 1, 4. 



Shell perforate, ovate-conic, thin, very minutely decus- 

 sated with growth-lines and spiral strias, slightly shining, 

 fulvous-whitish, diaphanous. Spire short, conic, rather ob- 

 tuse. Suture moderate. Whorls 4%, convex, the last five- 

 ninths the total length, rounded. Columella subplicate, reced- 

 ing. Aperture angularly oval. Peristome simple, thin, the 

 margins converging, right margin with a bell-like expansion, 

 columellar margin reflexed over the perforation. Length 15, 

 diam. 8%, aperture 9x6% mm. (Pfr.) 



Marquesas Is.: Dominique (Hivaoa), abundant on leaves 

 ( Garrett) . 



Bulinms decussatulus PFR., P. Z. S. 1849, p. 131. Partula 

 decussatula PFR., Monogr. iii, 453 ; Conchy 1. Cab. p. 274, pi. 

 65, f . 8, 9. EEEVE, Conch. Icon. pi. 4, f . 23. HARTMAN, 

 Catal. Gen. Partula p. 11, fig. ; Proc. A. N. S. Phila. 1885, 

 p. 217. GARRETT, Bull. Soc. Malac. France iv, 1887, p. 24. 



A thin, inflated species, yellowish-corneous slightly brown 

 tinted towards the summit, with a pale border below the 

 suture denuded of cuticle, and a narrow very faint brown 

 band just below the periphery. This band is sometimes very 

 inconspicuous. Old shells lose much of the cuticle, becom- 

 ing whitish and opaque. The aperture is ample. The peris- 

 tome is corneous, thin, well expanded but not thickened with- 

 in except in quite old shells. Several examples measure: 



Length 16.5, diam 10.3, aperture 10 mm., whorls 4%. 



Length 15.3, diam. 10, aperture 9.9 mm., whorls 



Length 15, diam. 9.9, aperture 9.9 mm., whorls 



The sculpture of rippled spiral striae is particularly well 

 developed in this species. 



