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Show 1904.] FROM EAST AFRICA A N D ZAXZIBAR. 401 CERATOSOMA CORNIGERUM*. [Bergh, Semper's Reisen, x. pp. 393 ff.; id.' Challenger ' Reports, pt. xxvi. p. 80 ff.] Numerous specimens of Ceratosoma, mostly found together and apparently belonging to one species, were captured at Chuaka in February 1901. About 40 of them were preserved. The living animals varied greatly in coloration, the ground-tint ranging from olive-green to deep chestnut-red, with gradations in each shade. On this ground were numerous dark brown spots and white mottlings in varying proportions, but it is to be noted that the variations in the ground-colour were real and did not depend on the markings. In all specimens there were a row of violet dots round the foot, and violet lines or spots on the head near the rhinophores, and generally near the branchiae as well. The ground-colour near the edge of the foot was white. One specimen was dark green with orange-yellow spots, and in all cases there were a few yellow spots near the edge of the foot and the genital orifices. Many of the animals were found in shallow pools, crawling over seaweed and in no way hiding themselves. They were sluggish in their movements, and had a peculiar, unpleasant, strongly aromatic odour. In many specimens the tail or the posterior-dorsal process appeared to have been bitten off. Possibly the carious shape may really be a protection to the animal by enabling it to escape with nothing worse than the loss of an unimportant part when it is seized by a carnivorous foe. No instances of self-mutilation were observed. The alcoholic specimens show considerable variation in size and proportions. Some are stout, some slender with relatively longer tails ; in some the lobes are much thicker than in others. Note was taken of one living specimen which had no lobes at all; another had two lobes like horns near the rhinophores. It does not appear that these variations in size and shape correspond with any differences in the radula, branchiae, or other organs. The measurements of an average fine specimen are as follows :- Total length 89 mm., tail 34 mm.; extreme height to tip of posterior lobe 33 mm., extreme breadth across lateral lobes 26 mm. The posterior lobe rises 10 m m . ahove the level of the back, and the lateral lobes project 6 m m . from the line of the sides. The pockets of the rhinophores and branchiae have slightly raised rims in some specimens, but not in all. The rhinophores are rather large ; the club bears about 40 perfoliations on each side, and is supported on a stalk about as large as itself. The branchiae are long and string-like; in nearly all the specimens they project from the pocket and are not retracted. The arrangement is * In my paper on Mr. Gardiner's collection of Nndibranchiata, in the ' Fauna and Geography of the Maldive and Laccadive Archipelagoes,' I inadvertently alluded (p. 552) to Ceratosoma polyomma as common in East African waters. I should have said C. cornigerum. |