AN ATTEMPT TO CLASSIFY EAETH WORMS. 231 



Genus 9. Trigaster, Benham, 1886 ( = Benhamia, 

 Michaelsen, 1889). 



Setae in four couples, all on the ventral surface; individual 

 setse of each couple close together. 



Clitellum occupies Somites xiv to xl ; complete veutrally 

 only on the first few somites. 



Spermiducal pores in xviii, and prostate-pores in 

 XVII and xix, in a large pit or fossa occupying the middle of 

 the ventral surface of Somites xvii to xx, the margins of 

 which are formed by two papillae. 



Sperm-sacs not observed. 



Prostates as in Acanthodrilus. No penial setae. 



[Prostomium not dovetailed into peristomium. No dorsal 

 pores are present. 



Spermathecae simple pear-shaped sacs without appendices, 

 opening close to mid-line on ventral surface. 



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

 glands. Anterior masses of nephridial tubules in Somites iv, 

 V, VI, grouped to form '' pepto-nephridia."] 



Species 1. T. lankesteri, W. B. B., 1886; St. Thomas, 

 West Indies. 

 2. T. rosea, Michaelsen, 1889 ; West Africa. 

 See Benham, ' Quart. Journ. Micr. Sci.,' xxvii; Michaelsen, 

 ' Jahrb. d. hamburgischen wiss. Anstalten,' vi, 1889. 



Genus 10. Deinodrilus, Beddard, 1888. 

 Setae twelve per somite, nearly equidistant. 

 Clitellum complete ventrally ; occupies only Somites xiv 



to XVI. 



Spermiducal pores, prostate-pores, sperm-sacs, &c., 

 as in Acanthodrilus. 



[Prostomium dovetailed into peristomium. 



Spermathecae with three small globular appendices, two pairs 

 in Somites viii and ix. 



A single gizzard occupies Somites vi, vii. No calciferous 

 glands. 



