228 FOURTH KEPORT — 1834. 



^sterias, Holothuria, and Siphunculus, sill which he has sub- 

 mitted to a close investigation. His researches on the genus 

 Siphuncuhis lead him to think that this group has been wrongly 

 placed by Cuvier in the present class, and that it belongs more 

 properly to the Annelida. 



In 1827, Mr. Thompson published an account of a newly dis- 

 covei-ed recent species of Pentacrhnis*, a genus well known in 

 a fossil state, but one of which the true situation in the system 

 was before rather doubtful. From an examination of this spe- 

 cies, the structure of which in its several stages of development 

 he has given in full detail, Mr. Thompson fully proved that the 

 Crinuidea (so ably illustrated by the late Mr. Millerf) are closely 

 allied to the Asterice, and especially to the genus Comatula of 

 Lamarck. The only previously known recent species of this 

 tribe, the P. Caput Medusts, found in the West Indies, had not 

 been brought to Europe in a fit state to allow of any investiga- 

 tion of its structure. 



Mr. Gray has lately submitted to the Zoological Society:}: speci- 

 mens of the shelly covering of a new genus, which is interesting 

 as forming a distinct family, if not order, intermediate to the 

 Echinidce and Asteriidce. It is allied to the latter in having 

 only a single opening to the digestive canal ; while it agrees 

 with the former in form and consistence, differing however from 

 it in not being composed of many plates. For this genus, which 

 Mr. Gray thinks bears a near affinity to the fossil Glenotremites 

 paradoxus of Goldfuss, he proposes the name of Ganymeda. 



In XheAnn. of Phil, for 1825 §, Mr. Gray has published a 

 natural arrangement of the families of the EchinidcB\\. 



2. Entozoa. — In this group, as it stands in the R^gne Animal, 

 we find an assemblage of animals which, though not much studied 

 in this country, have received great attention from several Ger- 

 man and French naturalists, from whose combined researches 

 it seexns now quite certain that they can no longer be arranged 

 all in the same class, Cuvier divides the Entozoa into two 



* Memoir on the Pentacrinus Europaus, Sfc. 4to, Cork, 1827. 



f Nat. Hist, of the Crinoidea, or Lily-shaped Anmah,8fc. 4to, Bristol, 1821. 



J Proceedings of the Zool.Soc. (1834), p. 15. § vol. xxvi. p. 423. 



II Since tliis Rejiort was read, a short but important communication on the 

 external structure of the Echinodermata and their mode of growth has been 

 published by M. Agassiz. His cliief object is to show that the Echinodermata, 

 although usually considered as partaking of a radiated structure in which all 

 the parts of the body are similar, nevertheless exhibit a bilateral symmetry ; 

 furthermore, that the addition of new plates, as the animal increases in size, 

 takes place in a spiral anA not in a vertical succession, as would appear at first 

 sit'ht to be the case. M. Agassiz announces it to be his intention to publish a 

 monograph on these animals. See Load, and Edinb. Phil. Mag. and Journ. oj 

 4'd. forNov. 1834, p. 3G9. 



