228 SIK. F. E. BBDDABD ON NEW EABTHWOEMS. [Mar. 19, 



Eisen allows three genera o£ worms where I only allow the 

 genus Microscolex. These genera are of course my Mhododrilus 

 and Eisen's Deltania in addition to Microscolex. Deltania is dis- 

 tinguished from both by the closer approximation of each pair of 

 ventral setae in the segments near to the xviith. Rhododrilus is 

 distinguished from both by the separate opening of sperm-ducts and 

 spermiducal glands. This latter character will hardly suffice as a 

 mark of distinction ; there are so many intermediate conditions in 

 the genus Microscolex (s. s.). In M. gracilis the two unite well 

 within the body-cavity ; in M. novce-zealandiw just at the common 

 orifice ; in M. ^xipillosiis the external orifices are separate but still 

 close together, in M, michaelseni at some little distance apart ; 

 finally in M. modestus, as I have an opportunity for stating here, 

 the pore of the sperm-duct is positively in the next segment to 

 that which contains the orifice of the spermiducal gland. Nor do 

 I admit that the approximation of the ventral setae in the genital 

 segments is a character of sufficient importance to imply generic 

 distinction. To begin with, M. diversicolor is somewhat inter- 

 mediate, the approximation being less marked. Then the species 

 of the genus are not all of them furnished %vith distant setae ; in a 

 good many of the South-American species the setae are strictly 

 paired ; this difEerence is itself of greater importance, I think ; and 

 the close pairing of the ventral setae in the neighbourhood of the 

 male pores is an intermediate condition between the paired setae 

 and the distant setae. If it is thought necessary to divide what I 

 here ca\l Microscolex into two genera, a more suitable line of division, 

 as it appears to me, would be to sepai-ate off those species in which 

 the testes and sperm-duct funnels are only one pair ; this division 

 would include all the new species described in the present paper 

 with the addition of Microscolex spatulifer, and would include all 

 the South- American forms, excepting only M. duhius and M. modes- 

 tus. I do not, however, propose even this division of the genus. 



Most of the new species differ from Microscolex modestus and 

 M. dubius, the types of the genus, in having a prostomium which 

 entirely divides the buccal segment, and in that the setae are 

 strictly paired. As, however, these two characters are not always 

 correlated, I do not think it possible to create any new genera. 

 Another interesting feature about some of the new species of 

 Microscolex is that, like M. spatulifer and many of the Acantho- 

 drilvs, they are very brightly coloured. 



The internal structure does not present much of great interest. 

 Indeed, the uniformity of the Cryptodrilidae as a whole is in striking 

 contrast to the greatly varied structure of the Eudrilidae, with 

 which I do not think that anybody now would venture to associate 

 them. 



(1) Microscolex griseus, n. sp. 



This species, like Microscolex spatulifer, is one to which the 

 generic name Microscolex is etymologically inapplicable. It is a 

 large species, nearly if not quite as large as Microscolex spatidifer. 



