1 84 Transactions of the Royal Canadian Institute 



Dendronotus arborescens (O. F. Muller). 

 Doris arborescens Muller, Zool. Dan. Prod., 229; Fab. Faun Groenl, V. I, 



p. 3107. 

 Tritonia arborescens, Cuvier in Ann. de Mus., V. 6, p. 434, pi. 61. Gould, 



Invert. Massach., p. 5. 

 Dendronotus arborescens Alder and Hancock, Mon. Brit. Nudib. Moll., 



Pt. I, 1845, Fam. 3, pi. 3. 

 Dendronotus purpureus Bergh, Proc. Ac. Nat. Sci. Phila., Pt. I, 1879, 



p. 88. 

 Dendronotus arborescens Bergh, Bull. Mus. Comp. Zool., Harvard, Vol. 

 XXV, 1894, p. 137. Eliot, Brit. Nudibr. Moll., Pt. VIII, 1910, 

 p. 161. 



Body. — The body is fairly long, higher than broad and with a well 

 rounded back. The dorsum is smooth and bears two series of much 

 branched dendriform papillae. The body is not sharply marked off from 

 the narrow foot. A veil is present bearing two median arbusculi and 

 three lateral ones on each side, diminishing in size as they pass out. 

 Between the median arbusculi is a distinct papilla. Beneath the veil 

 on the upper lip are a series of blunt papillae increasing in size as they 

 pass from the middle line. The tentacle sheaths {vide infra) appear some- 

 what similar to the arborescent papillae. These papillae are seven in 

 number on each side decreasing in size and complexity from before 

 backwards. The anus is situated on a small papilla between the first 

 and second papillae of the right side and bears at its foot a minute renal 

 pore. The genital aperture lies just below and in front of the first dorsal 

 papilla on the same side. 



Colour. — I have not yet seen these animals alive but preserved they 

 were of a dull opaque grey with the papillae of a dull brownish shade. 

 According to Alder and Hancock the colour of the species is subject to 

 considerable variation. 



Dimensions. — Bergh gives the measurements of his largest specimens 

 as 50 mm. long by 15 mm, high and 15 mm. broad. The larger of the two 

 specimens examined measured after preservation 20 mm. long by 8 mm. 

 high and 6 mm. broad. 



Head. — The head is not conspicuous and bears the transverse slit-like 

 mouth. 



Fooi. — The foot is elongated and narrow, abruptly rounded anteriorly 

 while posteriorly it terminates in a point. 



Rhinophores. — The clavus of the rhinophore is markedly perfoliated 

 having about 20 leaves on each side. The leaves are thin and alternate 

 in breadth . The rhinophore sheath is tall and bears at its apex 5 simple 

 dendriform projections and gives off another more complexly branched 



