360 NOTES ON SOME BRITISH NUDIBRANCHS. 



distinct l>ut short horns. The oral tentacles are moderately long, with 

 a few scattered opaque white dots. The rhinophores are long, wrinkled, 

 but not perfoliate, transparent and colourless, except that the tips are 

 covered with opaque wliite dots. The eyes are small, but black and 

 distinct. The cerata are set in five groups, composed on the right side 

 of three, four, two, four, three, and on the left of three, three, four, two, 

 three cerata respectively. These five groups are all seen to be distinct 

 when the animal is moving and stretched out. Otherwise the first and 

 second and the fourth and fifth a))pear to coalesce, though the third 

 always renuiins distinct. The general impression produced is that the 

 cerata are few and scattered irregularly. The innermost are the largest 

 and are rather swollen. The body is colourless and transparent. On 

 the tail is a line of irregular Ijright white spots. The yellowish-grey 

 hermaphrodite gland can be seen through the integuments. The 

 hepatic diverticula within the cerata consist of two elements, one bright 

 green, the other brownish yellow. As a rule the green predominates 

 and gives the general colour, but in some of the cerata the brown pig- 

 ment prevails. 



The jaws are thin and colourless, with at least six rows of denticles. 

 The radula consists of thirteen rows. The central tooth has as a rule 

 four denticles on each side of the median cusp, but sometimes five, and 

 only once six. The laterals have the apex turned inwards and bear 

 five or six denticles. 



A third specimen was dead when examined. Though much macerated 

 and mutilated, it appeared to have resembled the one just described 

 externally. The cerata were green with white tips. The radula con- 

 sisted of twelve rows. The central teeth have uniformly seven denti- 

 cles on each side of the median cusp. The laterals bear three to six 

 denticles. The tips of several laterals seem to point outwards. 



According to Alder and Hancock, who created both species, C. gracilis 

 has orange-red cerata and four denticles on the central teeth, whereas 

 C. smariKjdinii has green cerata and seven denticles. The second of the 

 forms described above appears to be intermediate both in colour and 

 dentition between C. gracilis and smaragdina, and suggests that the 

 animals in which the green pigment predominates should be called 

 C. gracilis, var. smaragdina. 



Vayssiere {liecherches sur les Moll. Opisth. dii Golfe dc Marseille, ii. 

 p. 76), regards C. laiulshurghii, C. rufihranchialis, 0. felluciday C. smarag- 

 dina, and C. gracilis as being all synonyms. This appears to me exces- 

 sive, as besides other characters the forms vary in their dentition. l>ut 

 it must be admitted that we require nmch more information to enable 

 us to judge how far the number of denticulations may vary within the 

 limits of one species. 



