Genera Trigaster and Benlianiia. 41 o 



agrees with Trujaster Lankesteri^ but differs in sevei-al of the 

 characteristic features of the hitter, one being the possession 

 of two gizzards and another the extent of the clitelluni. Dr. 

 Michaelsen, however, suggested the suppression of the uauie 

 Trigaster in favour of Bcn/tdniia, on the ground that the 

 former generic name no longer holds good for his new species 

 on account of its signiticanco. 



In my recent article, " An Attempt to Classify Earth- 

 worms ' (Quart. Journ. Micr. Sci. xxxii.), I have included 

 his species under the older name IVt'jister ; this I did 

 believing that, although the name had no longer a literal 

 significance for the new species, I was justified in retaining 

 the prior name. Dr. Michaelsen has published descriptions 

 of other species of the same genus, and after communication 

 with him and with Dr. Rosa, of Turin, and a careful perusal 

 of his papers, 1 am led to regard the species of Benhamia 

 as distinct from Trigaster. The two genera are not 

 synonymous, as would appear from his article, but are 

 distinct though very closely allied forms ; and perhaps they 

 should both be rei^arded as subu'enera of Acantkodrllas. At 

 present, however, I would consider them as distinct. 



The following characters are common to the three genera, 

 together with Deinodrilus (Beddard) : — 



(1) Nephridia in form of a network. 



(2) Two pairs of coiled cylindrical prostates in somites 



xvii. and xix. 



(3) Two pairs of spermathecae. 



Deinodrilus differs from the rest in possessing twelve setiB 

 per somite and in its short clitellum (xiv. to xvi.). 



Acanthodrilus has a single gizzard and behind it paired 

 calciferous glands. 



The anterior nephridia form a compact mass or pepto-neph 

 communicating (? always) with the pharynx. 



The spermathecffi lie in somites vii. and viii. 



The two sperm-ducts of each side are separate till near the 

 sperm-pore. 



Trigaster : — 



1. The clitellum is extremely long, occupying somites xiii. 



to xl. 



2. There are three separate gizzards, in somites vii., viii., 



and ix. 



3. There are no calciferous glands. 



