Appendix: Notes on the Anatomy of Streptostele (Raffraya) horei Smith

Apart from THIELE’s (1912) meagre notes on the anatomy of Streptostele, which chiefly concern the radula, and the fuller description of that of S. buchholzi v. Mts. by ODHNER (1932), little seems to have been published on any of the organs of the species belonging to this genus except the shell, although PILSBRY (1919) gave some account of certain of the internal organs of Varicostele bequaertiana Pils., a species belonging to a nearly related genus, which THIELE regarded as only a subgenus of Streptostele. I am therefore glad to be able briefly to describe some of the more important organs of Streptostele (Raffraya) horei Smith, based on spirit material from Yanonge in the Belgian Congo kindly submitted to me by Dr. VENMANS, who has dealt with the shell and distribution of this species in the preceding part of this paper. Skin and foot. — In specimens preserved in alcohol the skin is completely unpigmented, but it is sufficiently transparent for the black eyes to be clearly seen through it, even when they are deeply withdrawn within the head. The rugae are best developed on the top of the hinder half of the foot, where the furrows between them form oblique grooves sloping down on each side to the horizontal pedal groove. This is well marked, and cuts off a rather broad, clearly defined foot-fringe, which is crossed by small vertical grooves. The footsole is narrow and undivided; and the foot tapers to a point at the hind end, which is usually curved up in spirit specimens. No caudal mucous pore appears to be present.