122 OPEAS. 



Whether the form reported as introduced at Sydney is cor- 

 rectly identified as P. tuckeri I do not know; but it is more 

 likely to be Opeas gracile, 0. javanicum, or some of their 

 errant brothers. 



Genus OPEAS Albers, 1850. 



Opeas Alb., Die Hel., p. 175, first species B. siibula Pfr.- 

 HEEMANNSEN, Indicis Generum Malac., Suppl., p. 96, Dec., 

 1852, B. subula Pfr. mentioned as type. CEOSSE ET FISCHER, 

 Miss. Scient. Mex., Moll., i, p. 592; same type. MARTENS, 

 Die Hel., edit. 2, 1860, p. 265 (Stenogyra goodalli selected as 

 type). 



The shell is small, thin, turrite, usually perforate, with 

 large, obtuse, rounded apex and convex or flattened whorls, 

 corneous or yellowish. Embryonic whorls smooth. Aperture 

 small, ovate, the outer lip thin, usually arched forward, colu- 

 mella straight or concave, not sinuous, the columellar lip re- 

 flexed, curving into the basal lip and not toothed or truncate 

 below. Oviparous, the egg-capsules large and spheroidal. 

 Type 0. subula Pfr. (0. gracile Hutt.). 



Opeas contains small, thin, oviparous Stenogyrine snails 

 with the apex large, obtuse, rounded and smooth, and the 

 columellar margin reflexed, rounded below, or at least not 

 distinctly truncate. The species are spread throughout tropi- 

 cal and subtropical regions, but as yet none is known from 

 Australia. A few species colonize freely, and have spread 

 wherever commerce reaches in suitable climates. Others, re- 

 stricted to special stations not to be found in cultivated areas, 

 are as local as most other land snails. Owing to the similar- 

 ity of the shells, their determination is difficult, and demands 

 the greatest application. 



Opeas stands very close to the groups Prosopeas and 

 Curvella. The former differs by merely such minor features 

 as the rougher, often minutely iamellose sculpture, the greater 

 size and flatter whorls, but these give the shell a rather differ- 

 ent aspect. Curvella in its typical forms differs by the short 

 and Bulimoid shape ; but some of the species are arbitrarily 

 referred to one or the other genus. The distinction between 



