1834.] PROF. F.J. BELL ON THE GENUS AMPHICYCLUS. 253 



in the upper jaw being 30 millim. instead of 72 as in the adul 

 They evidently rep resent the narrow apical portion of the permanent 

 teeth, which as growth proceeds wears off, and they are not in any 

 case milk-teeth. As the first of the series, or premolar, is as fully 

 developed as the one which follows it (or first true molar) it must 

 either have no predecessor, or one which has disappeared at an early 

 stage of intra-uterine life. 



2. Studies in the Holothuroidea. — III. On Amphicyclus, a 

 new Genus of Dendrochirotous Holothurians, and its 

 bearing ou the Classification of the Family. By Pro- 

 fessor F. Jeffrey Bell, M.A., Sec.R.M.S. 



[Received March 28, 1884] 



Among the valuable collections made during 1876 by Captain 

 H. C. St. John, H.M.S. ' Sylvia,' in the Japanese seas were a few 

 Holothurians ; these were not reported on along with the rest of 

 the Echinodermata, which some years ago formed the subject of 

 interesting communications from Prof. Martin Duncan, F.R.S., and 

 Mr. Sladen l . 



Now that I am engaged in working through the collections of 

 Echinoderms in the British Museum, the Trustees of which owe the 

 specimens now under consideration to the generosity of Dr. Gwyn 

 Jeffreys, F.R.S., I think it proper to direct the attention of the 

 Society to two very remarkable specimens among these Holothurians 

 which cannot be placed in any genus at present instituted. The 

 lessons to be learned from these specimens, and the knowledge that 

 has been acquired of forms unknown to Professor Semper, thanks 

 chiefly to the labours of Ludwig and v. Marenzeller, lead, I think, 

 to a reconsideration of the classificatory system and phylogenetic 

 table which in 1868 was put out by Semper, to whom the student of 

 Holothurians will always be under the deepest obligations. It is with 

 diffidence that I propose to rearrange a family that has been studied 

 by this distinguished naturalist. 



Description of the Specimens. — Body elongated, tapering at its 

 hinder end. Oral tentacles in two cycles ; in the outer fourteen, of 

 fair size, and more or less subequal ; in the inner ten, very small, 

 arranged regularly by pairs, radial in position. Suckers confined to 

 the ambulacra, arranged in quite regular rows; in the bivial ambu- 

 lacra they are set in pairs, but are a little more irregular and more 

 crowded in the trivial ambulacra. Owing to the attenuation of the 

 body in the hinder region, the rows of suckers approach one another. 

 The interradii are altogether free of suckers. There are no signs of 

 any calcareous pharyngeal plates. 



1 Journ. Linn. Soc. (Zool.), vol. xiv. pp. 424, 445. 

 Proc. Zool. Soc— 1884, No. XVIII. 18 



