ANATOMY OF THE TEST OF DISCOIDEA CTLINDEICA. 61 



species. The validity of this interesting observation by Loven 

 will have to be tested on other grounds ; for it is a matter of 

 considerable doubt in our minds whether all the species which 

 have been admitted into the genus Discoidea can remain in it. 



D. suhuculus differs much from D. cylindrica in the hollowed-out 

 and tumid nature of the actinal part of the test, in the existence 

 of low primary ambulacral plates only, and their great crowding 

 without the formation of compound plates. Again, the madre- 

 porite is in the second basal only. Nevertheless, we have found 

 ribs on the inner surface of the actinal part of the test, as in 

 D. cylindrica ; and probably the perignathic girdle will be found. 

 As yet, we have only detected very indefinite traces of it. 



On the Characters of the G-enus Lopho^pus, with Description of a 

 new Species from Australia. By Stuaet O. Eidlet, M.A., 

 E.L.S. 



[Eead 4th November, 1886.] 

 (Plate II.) 



Peobablt in few groups of the Animal Kingdom have such 

 unnatural characters been employed for the distinction of genera 

 and species as in the Phylactolaematous Polyzoa, Few systematic 

 zoologists can, for example, have studied the relations of Alcy- 

 onella and Plumatella without feeling that the current reasons for 

 separating these two divisions are far from satisfactory, consist- 

 ing, as expressed by Prof. Allman in his well-known ' Monograph 

 of the Preshwater Polyzoa ' (Eay Society, 1856), chiefly in the 

 manner of connection between the tubes composing the colony. 

 " Except in the condition of the dermal system, the structure of 

 Plumatella differs in no essential point from that of Alcyonella. 

 This system, however, in the coalescence of the tubes into a 

 common mass in Alcyonella, while they remain totally distinct in 

 Plumatella, presents us with a difference which I believe to be 

 of sufficient importance to justify us in placing the two forms in 

 separate generic groups " (I. c. p. 92). 



Dr. Jullien Monographic des Bryozoaires d'eau douce," Bull. 

 Soc. Zool. I^rance, x. p. 90, published in 1885) has given very 

 forcible expression to this feeling of dissatisfaction, and has 

 indeed introduced into the classification modifications of a very 



LINN. JOUEN. — zoology, YOL. XX. 6 



