114 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
10. Halgerda rubra, Bergh. (= Selerodoris rubra, Hliot.) 
1). | H. mornata, Bergh, 1905. 
12. | H. coriacea (Eliot) 1903. These two species are probably identical. 
II. Sclerodoris, Eliot. Texture hard and rough, much as in Platydoris. Branchial 
pocket with lobes or teeth. External teeth of radula not pectinate in known 
species. 
Sel. tuberculata, Eliot. 
Sel. osseosa (Kelaart). 
3. Sel. minor, Eliot. 
B. An armature on the genitalia. 
Ill. Percnodoris, Bergh. Body rather hard. Branchial pocket toothed or tuberculate. 
IE, 
2. 
Inner teeth of radula sometimes with a few denticles. A stylet on the verge. | 
1. P. cancellata, Bergh. 
2. P. denticulata, sp. nov. 
IV. Asteronotus, Ehrerberg. Large animals with a texture resembling Halgerda. 
Branchial pocket strongly toothed. Teeth of radula not denticulate. Glandula 
et hasta amatoria near the female orifice. 
1, | A. hemprichi, Ehrenberg. 
2.4 A. cespitosus (von Hasselt). 
3.' A. mabilla, Bergh. These three species are probably varieties of one form. 
In the above arrangement I have regarded Dictyodoris as identical with 
Halgerda, and I doubt if my genus Sclerodoris will prove valid. After 
ereating it I withdrew it as probably equivalent to Bergh’s Peronodoris, 
which has priority. But perhaps it may be well to retain it provisionally. 
The stylet of Peronodoris is a more important character than an armature of 
spines and scales, which are little more than a thickening of the skin, for it 
represents more than they do the development of a new organ. Also the 
harsh rough texture of Sel. tuberculata and Sel. osseosa seems to me quite 
different from the texture of Halgerda. 
I regard my Sclerodoris rubra as certainly the same as Bergh’s Halgerda 
rubra, and my Sel. coriacea as being probably his Halgerda inornata. In 
excluding these species from Halgerda I was influenced by Bergh’s definition 
of the genus in the ‘ System der Nudibranchiaten Gasteropoden’ (. . . Tentacula 
parva... podarium sat angustum. Dentes pleurales extimi apice serrulati). 
But if that definition is made more elastic, I see no reason why these forms 
should not be included in Halgerda, except that my specimen of H. rubra has 
a hard rough torch unusual in the genus. 
This group of Dorids runs into Stawrodoris on the one side, for it is very 
hard to draw a line between forms which are typically tuberculate but have 
tle tubercles connected by ridges, and forms which are typically ridged but 
develop tubercles on the ridges. On the other side the group runs into 
Platydoris, such a form as Hoplodoris being intermediate between that genus 
and Asteronotus. 
