Genera Trigaster and Benhamia. 415 



agrees with Trigaster Lanhesteri^ but differs in several of the 

 characteristic features of the latter, one being the possession 

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

 Michaelsen, however, suggested the suppression of the name 

 Trigaster in favour of Benhamia, on the ground that tlie 

 former generic name no longer holds good for his new species 

 on account of its significance. 



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

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

 his species under the older name Trigaster] 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 regarded as subgenera of Acanthodrilus. 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 setce 

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



Acanthodrilus has a single gizzard and behind it paired 

 calcifcrous glands. 



The anterior nephridia form a compact mass or pepto-neph 

 communicating (? always) with the pharynx. 



The spermathecEe 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. 



toxl. 



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



and ix. 



3. There are no calciferous glands. 



