1879.] NATURAL SCIENCES OF PHILADELPHIA. 117 



leaflets.' The opening of the branchial cavity rather small (dia- 

 meter 1.5-2 mm.) round, not prominent, with a reflexed and 

 scarcely crenulated margin. The gill consisted of five tripinnate 

 leaflets,'-' the anterior median hardly smaller than the others. The 

 two anterior laterals were often cleft so as to simulate two plumes. 

 The anal tube was short, truncate, situated between the two pos- 

 terior branchial plumes, the renal orifice at the right side. 



The head was small, consisting of the mouth and two small 

 flattened tentacles, with a furrow along their outer margin. The 

 flattened genital papilla furnished with a rather contracted orifice; 

 in its upper part always a more or less (1.0 mm.) projecting trian- 

 gular or spoon-shaped lobe (figs. 21, 22). The foot straight or a 

 little rounded in the forepart, strongly grooved in the margin ; the 

 upper lip slightly cleft in the median line. 3 The peritoneum color- 

 less. The five individuals were dissected. 



The central nervous system showed the cerebral ganglia of 

 rounded-triangular, form, sometimes somewhat elongated, larger 

 than the visceral ones, which are more rounded. In connection 

 with the hind part of the under side of the right cerebral ganglion 

 was a small rounded ganglion (of about 0.07 mm. diameter) pro- 

 minent between the hinder part of the cerebral ganglia, and giving 

 off a long nerve backwards. In connection with the anterior part 

 of the upper side of the cerebral ganglion was an optic ganglion, 

 a little smaller than the former; the n. opticas rather short. In 

 connection with the posterior part of the under side of the visceral 

 ganglion through a rather short nerve is an oblong ganglion geni- 

 tale,* giving off a long nerve to the anterior genital mass (penis?) ; 

 the ganglion containing cells of rather unequal size. The pedal 

 ganglia are situated perpendicularly or oblique to the former, and 

 a little compressed. The commissure rather broad and short, as 

 long as the largest diameter of the pedal ganglion; the proximal 

 olfactory ganglion bulbiform, very short stalked, a little smaller 

 than the buccal ones. No true distal was observed. The visceral 



1 According to A. and H. the number of leaflets is twelve to thirteen, ami 

 to Meyer and Moebius fourteen. 



2 Both A. and H. and Meyer and Moebius mention five plumes. 



3 The markings on the under side of the mantle-brim (cf. Alder and Han- 

 cock, 1. c. fig. 2) were not visible. 



4 This ganglion had already been seen by Hancock and Embleton (1. c. 

 PI. XVII. fig. 9). 



