1879.] NATURAL SCIENCES OF PHILADELPHIA. 101 



the buccal ganglia (PI. IV. fig. 6) are rather large, of oval out- 

 line; the gastro-oesophageal rather short-stalked, ovoid, with three 

 large cells (fig. 6a). 



The eyes are as usual. 1 The otocysts about 0.2 mm. in dia- 

 meter contain about sixty round or oval otoconia, reaching from 

 0.025 mm. rarely to 0.04 mm. in diameter, many of them marked 

 with a few fine concentric lines. 2 The skin is almost free from 

 spiculae, they are almost entirely absent from the interstitial con- 

 nective tissue. 



The oral tube is rather short, about 6.0 mm. long, wide, with 

 the usual longitudinal folds. The bulbus pharyngeus is strong, 

 about 16.0 mm. long by 14.0 mm. broad and high. The form is 

 in general shorter and stouter than in the typical Tritonia. The 

 "muscle-plate" on the front side as in Tr. Hombergi. 3 



The jaws (PI. IY. fig. 7) shorter, broader, and higher than in 

 the Tr. Hombergi; the length of the united jaws was 12, the 



1 The eyes in Tr. Hombergi show black pigment and a yellow lens, they 

 are about 0.28 mm. in diameter.. The nervus opticus is about four times 

 as long as the cerebro-visceral ganglion, and issues from a small ganglion 

 situated near the pedal ganglion, giving out a nerve before reaching the 

 eye, and continued in a third nerve beyond the eye. Cf. Ihering, 1. c. 

 p. 174. 



2 Alder and Hancock did not discover the otocysts in Tr. Hombergi, nor 

 did I, but they were seen by Ihering. 



3 The bulbus pharyngeus of the Tritonise is, as also the tongue, very like 

 that of the Pleurophyllidim, but somewhat more flattened (cf. my Bidrag 

 til en Monographi af PleuropTiylliidieme, Naturh. Tidsskr. 3 R. iv. 1866, pp. 

 224-356). The lip disk at the bottom of the oral tube is as in those ; also 

 the thick muscular plate at the front of the jaws (cf. 1. c. p. 229), and with 

 the usual transverse groove. In two individuals of the Tr. Hombergi of 

 the length of 7.5 and 5.5 cm., the bulb. phar. had the length of 20 to 23 

 mm., a breadth of 12 to 15 mm., and a height of 11.5 to 15.0 mm., or the 

 length of the bulbus amounted to about one-third that of the body ; on the 

 surface of the bulbus were marked partitions nearly as in the Pleurophyl- 

 lidiidce; the sheath of the radula on the hinder and upper end of the bulbus 

 was distinct, but not prominent. The united jaws 23 to 24 mm. long, with 

 a breadth of 12 to 16, and a height of 6 to 7 mm. ; the breadth of the jaw 

 alone behind the articulation about 2.5, on the broadest part 6.75 to 7.0 

 mm. ; the free part of the proc. masticator. 1.5 to 2.0 mm. long ; the articu- 

 lation rather prominent in front ; nearly the posterior half of the cutting 

 edge is serrated, every denticle composed of several, more or less coalescent, 

 conical points, elevated about 0.16 mm, ; a deep furrow for muscular inser- 

 tion nearly parallel with the cutting edge. 



