DESCRIPTIONS OF GENERA AND SPECIES 643 



the describer of the species tells us, can be completely withdrawn into the anterior 

 part of the gut. Although this is also a character of Trichochaeta, the smooth setae 

 do not permit of the species being placed in that genus. The position of the oviducal 

 pores is most unusual. So too are the sperm-sacs of segments xv, xvi. As, however, 

 we are not unacquainted with exceptional differences, peculiar to one species, of this 

 kind, it is perhaps not a reason for excluding R. proboscideus from the genus 

 Rhinodrilw. 



Genus GEOSCOLEX, F. S. LEUCKART. 

 Syn. Titanus, PERRIER. 



DEFINITION. Setae paired, diverging posteriorly, ornamented. Sperm-sacs long, 

 one pair. No spermathecae. Sperm-duct opens on to exterior through, a 

 muscular sac. 



The genus Geoscolex was first described, as regards its external characters only, 

 by F. S. LEUCKART ; in his classical memoir upon the terrestrial Oligochaeta 

 PERRIER (3) instituted a new genus Titanus for a Brazilian earthworm, which 

 ROSA (31) subsequently showed to be even specifically identical with LEUCKART'S 

 0. maximus ; the reasons for accepting this identification will be gone into under 

 the description of the species 0. maximus. 



The main features which characterize the genus are mentioned in the above 

 definition; the principal distinction from any other of the New -World genera is the 

 existence of a terminal ' atrium,' through which the sperm-ducts open on to the 

 exterior ; unfortunately nothing whatever is known as to the histology of this organ. 

 Geoscolex is also the only genus of New -World Geoscolicidae, excepting Anteus in 

 which there are no spermathecae ; but this character is of less importance as the 

 spermathecae are absent from several species of earthworms, and from the genera 

 Siphonogaster and Criodrilus in addition to Anteus. The long and single pair of 

 sperm-sacs also occur in Pontoscolex and Trichochaeta. 



There are two species G. maximus and G. foryuesi. 



(i) Geoscolex maximus, F. S. LEUCKART. 



G. maximus, F. S. LEUCKART, Zool. Bruchst. Heft ii, 1841, p. 104. 

 Titanus brasiliensis, PERRIEK, Arch. d. Mus., 1872, p. 57. 



Definition. Length, four feet two inches. Clitellum, XV-XXIII. Sperm-sacs moderately 

 long. JIafj. Brazil. 



4 N 2 



