10 Mr. A. W. Waters on 



a bifurcation aiul a similar one jnst above anotlier bifurca- 

 tion ; in a second there is below each of two of the bifur- 

 cations a short ovicell ; still another has two long ovicells 

 on one internode. I have not found any oueciostomes on 

 the elongate ovicells, bnt on tiic shorter ones near a bifur- 

 cation there is a curved tube distal to the series. This is 

 the same as in /. radians and /. parasitica, Busk. INluch 

 stress has been laid upon the position of an ovicell, and it is 

 often stated it grows at a bifurcation, which is somewhat 

 misleading, for in this aud some other species it may grow 

 in any position. 



Idmonea atluntica lias much in common with /. radians, 

 both liave long straight branches showing a tendency to a 

 somewhat parallel growth, both have a large and long ovicell 

 of similar shape in a similar position. Canu and Bassler 

 have made a genus Mesonea for the latter, based on the 

 large dorsal pores called by Caini and Bassler tergopores. 

 D'Orbigny had made the genus Crisina for Idmonea forms 

 with large dor»al pores, and Cann and liassler now make 

 Crisina nonnaniana, d'Orb., the type of Crisina — Pergens * 

 having described and figured a lateral ovicell. The difference 

 in the dorsal surface is important, and it may be sufficient 

 upon which to found a genus, but we have not yet got 

 certain proof. 



The specimens of Idmonea parasitica. Busk, jnst referred 

 to, grows inside a mass of Entalophora intricaria, B., with 

 the zocEcia regular and not as straggling as shown by Busk. 

 It is just the same size as /. radians, the ovicell is in the 

 same position and the same size, and in both the ooeciostome 

 is a curved tube distal to a series ; on the other hand, there 

 are no large pores either on tlie dorsal or anterior surface, so 

 that, although similar in all other respects than the pores, 

 the one would be considered Idmonea, tlie other Crisina. 

 These puzzles show that classification still requires much 

 study. 



The important point is the similarity, and the question of 

 names is of secondary importance. 



The specimen from Naples, which I considered was 

 /. niarionensis, B., certainly corresponds with Busk's figure, 

 but now it appears to be utiantica and there does not seem 

 any reason for comparing it with Crisina hochstetteriana, 

 Stoliczka, which is probably I. radians, Lamk., and, in fact, 

 marionensis does not seem to be a good species. 



* Rev. des Bry. du Cr^t. fig. par d'Orb. p. 344, pi. xii. fig. 3 (1887). 



