1879.] NATURAL SCIENCES OF PHILADELPHIA. 91 



a little shorter than the longest diameter of the ganglia ; the gan- 

 glia gastro-cesophagalia in size were about one-eighth of the last, 

 rounded, with a very large cell and several smaller ones. The 

 commissures, as in the D. arborescens. 1 



The eye was as usual, the pigment black. 2 The otocyst of the 

 diameter of about 0.1 mm., crowded with otoconia of very (from 

 about 0.004-0.0255 mm.) varying size. The leaves of the club of 

 the rhinophoria without spicula, and also the skin of the body, 

 which is easily detached from the subcutaneous muscular layer; 

 on the dorsal papillae especially, were masses of small yellowish 

 sac-shaped glands containing fatty matter. The anal tube was 

 short and wide, with longitudinal folds; the bulbus pharyngeus 

 formed as in the t3 T pical species, 5.0 mm. long, 3.0 high, and 3.0 mm. 

 broad. The insertion of the oesophagus was before the middle of 

 the upper side. The labial disk or ring strong, radiately furrowed, 

 of deep brown color internally; this inner portion formed a narrow 

 prehensile collar, composed of rather irregular closely and ob- 

 liquely set erect (fig. 18-20) spines, somewhat like those of the 

 labial plates in so many Dorididde, of dirty light yellowish-brown 

 color, 3 and about 4. mm. in height. 



The mandibles were yellowish-horn color, except that the arti- 

 culation was very dark-brown ; the form was exactly as in the typi- 

 cal 4 and in the following species (cf. PI. III. fig. 2-3). 



The processus masticatorius was rather short (fig. ta), with a 

 single series of small denticles exactly as in the D. arborescens 

 (PI. II. fig. 13 ; PI. IY. fig. 1); the cavities behind the articulation 

 of the mandibles were rather large (PI. III. fig. 3). The tongue 

 exactly as in the typical and in the next species (cf. PI. II. fig. 9, 

 10); the tectum (fig. 9a) radulse much extended forwards, and 

 the superior (fig. 10a) part of the rasp therefore very short; the 



1 The visceral commissure has not hitherto been seen even by Ihering 

 (1. c, p. 176) ; it is the foremost of the commissures, rather thin, the iV. 

 genitalis very distinct. 



2 In the Dendron. arborescens the end of the n. opticus is sometimes black. 



3 A similar somewhat broader collar was found in the larger specimens of 

 B. arborescens, but whitish like the rest of the labial disk, the spines (PI. 

 IV. fig. 2) were in more numerous rows (they hardly exceeded twenty in 

 D. purjmreus), and were light yellowish and longer. In two smaller indi- 

 viduals no trace of the collar could be found. 



4 Cf. my above cited paper, Tab. XII. fig. 28-30. 



