358 MR. F. E. BEDDARD ON [May 3, 



present species, however, there is no doubt of their lying in the xth 

 segment. 



The sperm-sacs are in segments x. and xi. They partially involve 

 the testes and vas deferens funnels. The ovaries are, it is almost 

 unnecessary to state, placed in segment xiii. The oviducal funnels 

 open opposite to them ; the ovaries are so large that but little room 

 is left between the end of the ovary and the funnel ; I saw an ovum 

 "within the mouth of the oviduct. There are no egg-sacs. The 

 oviducal pores are upon the xivth segment. 



In the viiith and ixth segments are the spermatothecse. These 

 organs are large sacs, communicating with the exterior by means of 

 a comparatively long duct ; they were densely packed with sperma- 

 tozoa, but had no diverticula. 



It is evident from the above short and, in some respects, incom- 

 plete account of the Pilcomayo worm that it is most nearly allied to 

 the genus Acanthodrilus. That genus, it should be remarked, is 

 one which is less uniformly terricolous than any other genus of 

 " earthworms." There are already several species known to occur 

 in water. Among them are Acanthodrilus stagnalis, A. dalei, 

 A. schmardce. This is, however, the first species which has been 

 met with in saline waters. 



The other aquatic Acanthodrilidae show no particular affinities to 

 aquatic genera ; but the present species does ; and it distinctly 

 approaches Ocnerodrilus. The resemhlance is not only in the sim- 

 plification of the structure of the atria ; that of itself would not 

 perhaps be a very important fact, since it might be put down merely 

 to degeneration. A more important point of likeness is the existence 

 of the single pair of oesophageal diverticula in segment ix. ; this par- 

 ticular segment is not a usual one in which to find these calciferous 

 glands. Besides, in other Acanthodrilids there are nearly always 

 two or three pairs of these glands situated further back. 



Very little is wanting to convert the species here described into 

 an Ocnerodrilus ; to refer it definitely to the genus Acanthodrilus 

 would be to ignore the characteristic differences which it shows from 

 that genus, with which, however, it undoubtedly agrees in all those 

 points which are made use of to define the genus Acanthodrilus. 

 On the other hand, it can hardly he put in the genus Ocnerodrilus. 

 The principal difficulty in the way of this is the two pairs of atria 

 and their position. The fact of there heing two pairs of atria 

 instead of one only would not deter me from this step ; I think, for 

 instance, that the genus Neodrilus must be merged in Acanthodrilus. 

 The important difference appears to be the separation of the atrial 

 and vas deferens pores by a septum in Acanthodrilus. If it were not 

 for the position of the calciferous glands all the resemblances between 

 this worm and Ocnerodrilus might fairly he set down to a con- 

 vergence due simply to degeneration. As it is I am inclined to 

 think that it will be necessary to institute a separate genus for this 

 Acanthodriloid worm from the Pilcomayo ; and I propose to call 

 it Kerria, after Mr. Graham Kerr, vdth the specific term halophila. 

 It may be useful to compare, by means of the following table, the 



