264 Transactions of the Society. 



phageal portion, each occupy two segments, 7-8 and 9-10. Behind 

 the gizzards, in segments 15, 16, 17, are calciferous glands, the 

 hindmost pair smaller than the two anterior pairs, and divided into 

 distinct lobes. Testes in 10 and 11, with vesiculie seminalis, and 

 funnels. Ovaries in 13 large and conspicuous with oviducts. 

 Each spermatheca divided into two parts— a sac or ampulla, and 

 a mulberry-like diverticulum. Length about 100 mm., from the 

 island of Fiji. 



Later, Beddard {^) defined the genus, which had in the mean- 

 time been studied and extended by Michaelsen, thus : — 



" Genus Dichogaster Beddard. Setie paired. Dorsal pores 

 present. Clitellum xiii-xx (xxiii). Male pores on xvii. Two 

 gizzards ; three pairs of calciferous glands. Nephridia diffuse. 

 Sperm iducal glands tubular." 



The difficulty in defining the genus was admitted, and with 

 Michaelsen's new species r/iimtis and hvpferi it was hard to say 

 how it could be distinguished from the allied genus Microdrilus. 

 In 1886 Benham (JJ) founded the genus Trigaster for a worm found 

 in the West Indies {T. lankestcri), and later {4) in 1890 defined 

 the genus (which had meanwhile received a new addition in 

 ]\Iichaelsen's T. rosea) as follows : — 



"Genus Trigaster Benham, l^^i^ { = Benhamia Michaelsen, 

 1889). Setre in close couples, all on the ventral surface, individual 

 setae of each couple close together. Clitellum occupies Somites xiv 

 to XTi ; complete ventrally only on the first few somites. Spermi- 

 ducal pores in xviii, and prostate pores in xvii and xix. . . . 

 Prostates as in Acanthodrilus. No penial setse. No dorsal pores 

 are present. Spermathecfe simple pear-shaped sacs without 

 appendices, . . . Three gizzards in Somites vii, viii and ix. No 

 calciferous glands. Anterior masses of nephridial tubules in 

 Somites iv, v, vi grouped to form peptonephridia." 



In his Monograph of the Order Oligocha^ta (2) Beddard separates 

 the two genera Dichogaster and Trigaster by a great distance, but 

 places Trigaster in close proximity to Bcnhamia. Indeed, the 

 two genera show many points of divergence. Yet Michaelsen (10) 

 in his volume on " The 01iQ;och?eta " makes the two genera into a 

 sub-family which he names Trigastrinje. One might question the 

 propriety of this, but that is a matter of opinion. The sub-family 

 is distinguished by the following marks : — Setie 8 per segment, 

 girdle extending over 4 to 27 segments, and beginning on or near 

 segment 14. Male pores on 18, 17 or 19, prostate pores on 17-19. 

 One or two pairs of spermathecre opening in 7/8, 8/9. Two or 

 three muscular gizzards in advance of the male organs, and three 

 pairs of calciferous glands usually present at the posterior end of 

 the oesophagus. 



The main distinction between Trigaster and DicJiogaster is said 

 to lie in the latter relation. Trigaster has no calciferous glands 



