448 RECOED OP CURRENT RESEARCHES RELATING TO 



Torres Straits, wliich illustrate this point very completely ; and it is 

 therefore of no small interest to find a fossil Comatula which shows 

 one of the extreme stages of the metamorphosis. 



The large size of the three Antedon species from the chalk and 

 gault is very remarkable. Ant. paradoxus has a centrodorsal half as 

 wide again as that of any recent form ; while Ant. EscJirichtii is the 

 only recent species with a centrodorsal approaching the size of those 

 of the other chalk Antedon, and of that from the gault. Act. Loveni 

 from the gault, however, and the older Comatulfe, all had small 

 calices like most recent species. An elegant centrodorsal (Ant. 

 rotundus') is described from the Haldon greensand, and also two 

 species from the Bradford clay. One is an Antedon, the oldest 

 known, with no special characters ; the other is an Adinometra, with 

 a centrodorsal essentially like those of species now living in shallow 

 water in the Philippines and Malay Archipelago. The oldest known 

 Comatula, an Adinometra from the Bath oolite, has similar relations. 



Synthetic Starfish.* — Under the name of AstropMura permira, 

 Mr. W. Percy Sladen has described a most remarkable form of Echino- 

 derm from the coast of Madagascar. While the ordinary starfishes 

 present usually the well-known starlike form, with five or more rays 

 springing from a central body, with which they are perfectly conti- 

 nuous, the body in the Ophiurids is a rounded or more or less pentagonal 

 disk, from which issue five jointed arms, quite distinct in structure 

 from the disk, and from the much stouter rays of the ordinary star- 

 fishes. Ml'. Sladen's new form combines the characters of the two 

 groups in a very singular manner, and, curiously enough, it is towards 

 the somewhat aberrant forms of starfishes (such as Goniodiscus), in 

 which the enlargement of the disk and shortening of the rays converts 

 the whole body into a pentagonal disk, that the new type seems most 

 to approximate in outward appearance. In fact, the arms are for the 

 greater part of their length enclosed in a disk formed of calcareous 

 plates, both above and below ; but a small portion of jointed arm 

 projects from each angle of the pentagon thus formed, and with the 

 structure displayed along the lines of the arms on the lower surface 

 sufliciently demonstrates the Ophiuridan afiiuities of the organism. 

 By careful study, indeed, Mr. Sladen makes out that the whole skeletal 

 structure is due to an abnormal development of the ordinary plates of 

 an Ophiurid, but at the same time he recognizes in the structure of the 

 animal a number of characters which tend towards the Asteroida, 

 such as a great development of the ambulacral system, with formation 

 of supplementary plates separating the tentacular compartments, the 

 extension of the peritoneal cavity into the radial portions of the 

 animal, and the organization of the mouth. 



Teeth of the Echinoidea. f — Herr Giesbrecht finds that the 

 structure of the teeth of the Echinoidea is very different from that of 

 the test or of the spines ; these latter are composed of a calcareous 



* 'Aim. and Map. Nat. Hist.,' iv. (1879) p. 401 (1 plate); sec 'Pop. Sci. 

 Kev.,' iv. (1880) p. 102. 



t ' Morphol. Jahrbuch,' vi. (1S80) p. 79. 



