MALACOZOA. GASTEROPODA. PECTINI3RANCHIATA. 57 



gated, the apex mammillifonn, the aperture roundish, 

 ovate, or pyrate, with the anterior end rounded, the pos- 

 terior acute ; operculum horny. Named after M. Risso, 

 a naturalist of Nice. Freminville. 



1. Rissoa ulvce. Shell oblongo-turrite, rather thick, 

 opaque, the spire elongated, the turns seven, flat, ob- 

 scurely striate transversely, the last convex and more or 

 less angulate. Ulva, sea- weed, from its living in salt 

 marshes. 



2. Rissoa muriatica. Shell oblongo-turrite, rather 

 thin, transparent, the spire elongated, the turns six, 

 slightly convex, faintly striate transversely, the last well- 

 rounded. The name refers to its living in salt water. 



3. Rissoa ventricdsa. Shell ovato-turrite, of five or 

 six thin, pellucid, glossy, convex, slightly striate turns ; 

 aperture roundish-ovate, more than a third of the whole 

 length. Ventricdsa, bellying or bulging. 



4. Rissoa pdrva. Shell ovato-turrite, rather thick, 

 nearly opaque, glossy, of six rounded turns, with strong, 

 convex, slightly waved, transverse ribs, those of the last 

 turn not reaching the aperture, which is roundish ovate, 

 the outer lip thickened externally. Pdrvus, small. 



5. Rissoa alba. Shell ovato-turrite, rather thin, semi- 

 transparent, glossy, of six rounded turns, with short, 

 convex, slightly waved, transverse ribs, those of the last 

 turn not reaching more than half-way; the aperture 

 roundish, the outer lip thin. Albus, white. 



6. Rissoa semistridta. Shell ovato- conical, pellucid, 

 spirally striate, glossy, of five rather convex turns, the 

 last sulcato-striate anteriorly, white, with two rows of red 

 spots, aperture roundish ovate, outer lip thin. Semi- 

 striatus, half-striated. 



7. Rissoa interrupta. Shell ovato-conical, pellucid, 

 smooth, glossy, of five rather flat turns, white, with a 

 spiral series of reddish-brown oblong spots near the 

 upper margin of each turn, and a band on the last. The 

 name has reference to the broken or interrupted reddish 

 band. 



8. Rissoa reticuldta. Shell ovato-turrite, rather thick, 



