RiTTEB. — Octacnemus. 



PLATE 1. 



Fig. 1. Dorsal view, natural size, of Octacnemus herdmani. The radial muscle 

 fibres in each muscle do not in general diverge quite as much toward 

 their insertion on the mantle as this figure indicates. 



Fig. 2. Ventral view of the same specimen. The oral disc as marked by the 

 ventral flange is somewhat too broad. 



