204 MR T. J. EVANS ON 



(7) The segregation of the genital elements of the visceral into a distinct ganglion 



on the surface of the brain. 



(8) The possession of a proximal and a distal rhinophorial ganglion. 



(9) The cuticularisation of the wall of the alimentary canal as far as the stomach 



(the horny cones imbedded in the cuticle were described by Eliot for B. 

 hodgsoni, but no armature was found by Bergh in B. abyssorum and B. 

 ingoljiana ; its systematic value cannot therefore be assigned). 



(10) The presence of a gastric csecum. 



(11) The presence of small otocysts below the pleuro-pedal connective. 



The genus may now be defined in the following terms, of which some are supple- 

 mentary to Bergh's original definition : — 



Body highly arched and elliptical in outline. The edge of the notseum slight or 

 wanting. Dorsal papillae present or absent. Ehinophores placed rather far back, non- 

 retractile, perfoliated. Gills in front of the anal papilla, variable in number, non- 

 retractile. Buccal mass very bulky. Radula sac not an appendage. Dental formula 

 n. 1. n. Buccal cavity with a thick cuticle extending down the oesophagus. Powerful 

 jaws present. (Esophagus may have horny cones. Liver massive and unlobed, not 

 invaded by any other viscus. Salivary glands follicular, flattened, with a stout 

 duct. Cerebral and pleural ganglia distinct. Stomatogastric loop very long. No 

 gastro-cesophageal ganglia, but the long gastro-oesophageal loop arises from the 

 buccals. Eyes absent. Kidney saccular with laminate ingrowths of its ventral wall. 

 Branchial and pallial efferents join before entering the right side of the auricle. Penis 

 unarmed and massive. Hermaphrodite gland a compact mass. Reproductive system 

 diaulic. 



The Affinities of Bathydoris. 



Bergh and Eliot have invested Bathydoris with a certain importance as a type 

 combining the features of the Dorids with certain Tritonid characters, with prepon- 

 derating affinities to the Dorids. The Tritonid features accentuated by Bergh were 

 the buccal apparatus and the unarmed penis, while Eliot rightly passes over the latter 

 resemblance unnoticed, since an armature of the penis may be present or absent among 

 the species of some genera of Dorids. As to the buccal apparatus, even a superficial 

 examination shows that, when reference has been made to the great size of the buccal 

 muscles and the jaws, the sole resemblance has been stated in full. In Tritonia the 

 odontophoral mass arises from the dorsal wall of the buccal cavity and bulges down- 

 wards, while in Bathydoris that organ arises from the floor of the buccal cavity and 

 bulges upwards. The mandibles are also quite differently placed and used in the two 

 animals, those of Tritonia having their long, finely serrulated cutting edges facing the 

 floor of the mouth cavity below the radula mass, while the blunt beaks of the mandibles 

 of Bathydoris jut into the mouth above the radula. Moreover, the oesophagus takes 

 its origin on the hinder aspect of the globular buccal bulb of Bathydoris, while the 



