MOORE : ON BATHAWALIA AND T3YTH0CEEAS. 



93 



2. Btthoceeas ieidescens, Moore. Fig. I. 

 JBythoceras iridescens, Moore : Proc. Hoy. Soc, vol. Ixii (March, 1898), 



p. 452, fig. 1. 



Shell ovato-fusiform, semi-solid ; colour ochraceous-brown, last 

 whorl darker ; whorls 1 \\, apical whorls smooth, second whorl 

 with spiral lirae, no ribs, protoconch heterostroph, whorls strongly 

 sculptured, bearing 15-17 nodulous spiral lirse, the 6-7 upper lirae 

 being especially nodulous, nodulations of different lirse coinciding 

 and forming transverse rounded ribs, the ribs in the younger whorls 

 and in the upper part of the last whorl being very pronounced and 

 obscuring the spiral lirse ; sutures channelled ; mouth in adtilt oval 

 with continuous thickened whitish-iridescent lip, produced both 

 anteriorly and posteriorly into a solid spine, the posterior spine is 



Fig. I. — Bythoceras iridescens, Moore. 

 ,, II. — Bathanalia Howesi, Moore, with operculum. 



especially strongly developed and may curve outwards, is triangular 

 in section but slightly excavated on its lower surface, the anterior 

 spine is less developed. In old specimens the oval lip is continued, 

 and projects slightly beyond the plane of the spines, in young 

 specimens both the spines and the thickened lip are wanting, and 

 the mouth is then somewhat larger, thin-edged, and elliptical. The 

 brownish periostracum is very thin, like that of Nassopsis and Para- 

 melania ; operculum as in Faramelania and Typhohia. It is, however, 

 most remarkable that this form bears no anatomical resemblance to 

 Nassopsis, being much more like Tanganyicia riifofilosa. The specific 

 name was chosen fi'om the peculiar yellowish pearly layer lining the 

 mouth and interior of the shell. 



Bythoceras was dredged living in 600-700 feet, near Sumbu, Lake 

 Tanganyika. 



