DESCRIPTIONS OF GENERA AND SPECIES 445 



four or five is the usual number. Papillae are constantly met with in the 

 neighbourhood of the male genital pores. 



As regards internal structure, there is a tolerable uniformity, less marked, it is 

 true, than in the Lumbricidae, but more marked than in the Geoscolicidae or 

 Eudrilidae. Neither the alimentary tract nor the vascular system call for any 

 particular comment ; they are both much as in the Perichaetidae, though the 

 caeca, so characteristic of that family, are only met with in the genus Millsonia. The 

 nephridia are found in three chief variations ; the most common, perhaps, is the 

 diffuse form of the excretory organs limited to this family, to the Acanthodrilidae, 

 and to the Perichaetidae ; in a large number of other species there are regularly 

 paired nephridia, which may, even in a few species, show an alternation, as in 

 certain Acanthodrilidae ; Plutellus has nephridia of this kind and also Cryptodrilus 

 fletcheri ; the third form in which the nephridia are developed is very remarkable ; 

 in a few species referred by me to the genus Trinephrus there are three distinct pairs 

 of these organs. The male ducts invariably open on to the exterior in common 

 with, or in the immediate neighbourhood of, spermiducal glands, penial setae 

 being very frequently present ; the spermiducal glands are, as in the Perichaetidae, 

 of two kinds ; there are either the lobate glands of Cryptodrilus or the tubular glands 

 of Megascolides ; in Trinephrus fastigatus there are two pairs of these glands, and in 

 Dichogaster damonis the single pair which are connected with the male ducts are 

 followed by two other pairs in as many consecutive segments. The spermathecae 

 of this family are nearly always furnished with diverticula ; it is only in some 

 of the small and degenerate (?) types that diverticula are absent ; the spermathecae 

 are paired structures (except in Fletcherodrilus, where they are in a single median 

 series), and the number of pairs varies from one to five; they lie anteriorly to the 

 testes. 



The headquarters of the Cryptodrilidae is, perhaps, the Australian continent ; a large 

 number of species have been described from that country by FLETCHER and SPENCER. 

 These belong to the genera Megascolides ( = Notoscolex), Cryptodrilus, Fletcherodrilus, 

 Trinephrus, and Digaster, all of which genera are nearly confined to that part of 

 the world. 



The two first- named are not at all easy to distinguish from each other. 

 'Notoscolex' was thus defined by FLETCHER (1, p. 546): 



' Intraclitellian worms with clitellum, comprising some or all of the segments 

 xiii-xxiii ; male pores two, on segment xviii, on papillae in a line with the intervals 

 between the inner couples of setae ; oviducal pores on segment xiv ; setae in eight 

 longitudinal rows.' 



