MOLLUSCA OF PLYMOUTH. 445 



wliicli Prof. Stewart found upon Hymeniacidon sanguineus (cf. my 

 previous Eeport^ p. 177) were large specimens of this species. 



Another specimen^ half an inch long, was again dredged on the 

 same ground early in June. 



It is important to prevent any confusion between this species and 

 Doris (Rostanga) coccinea, which is also red in colour. The best 

 character by which to distinguish them at once is the structure of 

 the anterior portion of the foot : inflammea this is entire, and separated 

 from the rest of the foot by a transverse groove only ; but in coccinea 

 it is split into two lateral portions, as in Doris (Jorunna) Johnstoni 

 and Doris (Platydoris) planata. Alder and Hancock's two specimens 

 were dredged in shallow water, Rothesay Bay, adhering to Pecten 

 opercularis. Prof. Ed. Forbes dredged it off the Isle of Man in 25 

 fathoms. Dr. Norman has also found the species at Cumbrae, and 

 Mr. Cocks recorded it in 1849 as '"^ very rare, on stones at extreme 

 low-water mark, spring-tide," at Gwyllyn Yase, Falmouth. 



27. Jorunna, Bergh. 



39. *JoRUNNA Johnstoni, A. and H. {= Archidoris Johnstoni, 1st 



Rep., p. 177.) 



Three more specimens of this species have been obtained. One, 

 half an inch in length, was found under a stone in a pool at Rum 

 Bay on March 7th, and was very sponge-like and inconspicuous. 

 Mr. Bourne also found two specimens on the shore at Wembury 

 Bay, one early in May, and the other a month later. 



The dark spots on the back of this animal have been constantly 

 present, but very variable in position ; they have the effect of ren- 

 dering the darkly coloured rhinophores less conspicuous. 



28. Platydoris, Bergh. 



40. ^Platydoris planata. Alder and RancocJc (= Archidoris planata, 



1st Rep., p. 178.) 



Two additional specimens have been taken. One, found at Drake's 

 Island, August 14th, 1889, measures (preserved in spirit) 1| inches 

 long by -j^ broad. The gill-plumes are six in number, the third 

 on each side being deeply bifurcated. They were completely re- 

 tractile, and when protruded appeared to be composed of two distinct 

 lateral halves. The underside of the pleuropodium and the foot 

 were orange-coloured ; the pleuropodium in life was often upturned 

 at the edge, showing its orange-coloured under-side. The radula 

 of this specimen is very abnormal, there being three longitudinal 

 series of great irregular teeth formed by the fusion of several of the 

 slender normal ones. On one side two teeth in each row are thus 



