360 SIR C. ELIOT ON KUDIBEAKCHS [DeC. 1, 



prostate is present in both Discodoris and Platydoris, which are 

 otherwise so distinct, and is absent in Archidoris but present in 

 Anisodoris, which are otherwise identical, (iii.) In many genei'a 

 is present an armature of the reproductive organs, that is, one 

 or many spines, hooks, or plates generally only on the male 

 branch. The value of this feature, as estimated by the con- 

 comitance of other important characters, varies. In the families 

 of Doridopsidfe and Phyllidiadee and in the well-marked genus 

 Platydoris of the Cryptobiunchiata an armature is, so far as we 

 know, charactei'istic. On the other hand, we find two genera 

 like Diaidula and Gargamella appai'ently identical but for its 

 presence or absence. In the Aeolidiadse also a hook or spine is 

 present or absent in closely allied genera. It appears to me that 

 such an armatui-e is not sufficient to constitute generic rank 

 without other characters, 



(/) The other internal organs do not offer many features 

 which serve our purpose of classification. It does not appear 

 that we can unite the forms in which the stomach is enclosed 

 in the liver, or in which there is only a single instead of a 

 double blood-gland, or in which the nervous sj^stem is very 

 concentrated. 



As a result of these considerations, I think that the most pro- 

 fitable way of classifying new Dorids of the group treated of here, 

 is to refer them when possible to the following genera taken in a 

 wide sense : — Archidoris, Discodoris, Thordisa, Trippa, Hcdgerda, 

 Kentrodoris, Platydoris, Asterotiotus, and Sclerodoris (gen. n.)* 

 No doubt, remarkable forms have been and will be found which 

 require special genera for their accommodation, but the majority 

 of species seem to me to fall under one or other of the divisions 

 mentioned. 



Archidoris is distinguished by a fairly plump shape, broad foot, 

 and a warty or tuberculate back. No member of this group is 

 known to possess a labial armature, and a genital armature is 

 rare. The radula generally consists of uniform, simply hamate 

 teeth : more rarely some or all are denticulate. I include in 

 this genus, in its wide sense at least, Anisodoris, Homoiodoris, 

 and ArtachcBU: As meiitioned above, though it is easy to define 

 the generic characters of a typical Staurodoris, the genvis seems 

 to pass into Archidoris by a complete series of connecting links. 



Discodoris. — I should be inclined to extend this genus so as to 

 mean flat, oval animals, not haicl, with both foot and mantle- 

 brim fairly broad. Back granulate. A genital armature is 

 usually absent ; a labial armature is either pi-esent (Section 

 Discodoris) or absent (Section Peltodoris). 



Thordisa. — Flat, soft animals, much like Discodoris, but with 

 the back neither granulate nor warty, but covered with soft 

 pointed papillse. No member of this group is known to possess 

 a, well-developed labial armature, though a rudimentary one is 

 found in Th. crosdandi. 



