DESCRIPTIONS OF GENERA AND SPECIES 175 



Hypogaeon hirtum, SAVIGNY. 



H. hirtum, J. C. SAVIGNY, Syst. d. Annel., p. 104. 



The chief peculiarity of this species, which was met with in the environs of Philadelphia, 

 is the nine parallel rows of setae. These setae are described as long, covered with spinolets, 

 particularly upon the clitellum, where their distribution is described as confused. This suggests 

 my genus Trichochaeta; but this suggestion is not supported by the position of the clitellum 

 (xxvi-xxxix), the male-pores (?) on xv and the spermathecal pores (?) on x, xi, xii ; it is impossible 

 even to guess at its position. 



Hypogaeon atys, KlNBEBG, might belong to any family ; it has eight setae per segment and is 

 32 mm. long. 



Another doubtful form, concerning whose position in the system nothing positive can be said, is : 



Alma nilotica, GRUBE. 



Alma nilotica, GRUBE, Arch. f. Naturg., 1855, p. 129. 



Digitibranchus niloticus, LEVINSEN, Vidensk. Meddel., 1889, p. 321. 



I do not give any systematic description of this worm, since its position in the series is very 

 doubtful. GRUBE, its original describer, does not give sufficient particulars to permit of a certain 

 opinion as to its relations, but compares it with Rhyncnelmis (' Euaxes'). The illustration (GRUBE 

 3, PI. v, fig. n) represents a worm of the thickness and length of a moderately-sized earthworm, 

 its measurements are given as 3-6 inches. During life it was, according to ROpPEL's notes, 

 who was the discoverer, red coloured ; it was found in the Nile mud. The most remarkable 

 peculiarity of the worm is the possession of branchial processes upon the posterior segments of the 

 body ; it is the presence of these structures which have led most writers to exclude it from the 

 Oligochaeta altogether, or, at least, to consider its Oligochaetous affinities doubtful. As we are now 

 acquainted with three undoubted Oligochaeta (viz. Chaetobranchus, Hesperodrilus, and Branchiura) with 

 branchiae, there is no longer any reason, on these grounds, to refuse admittance to Alma among the 

 Oligochaeta. LEVINSEN'S Digitibranchus niloticus must, in my opinion, be regarded as generically, as 

 well as specifically, identical with Alma nilotica; it was described from a fragment only, but so far 

 as this fragment enables one to judge there are no differences from the worm described by GRUBE. 



The branchiae occupy the last sixty segments of the body (as in Branchiura), they lie just above 

 the dorsal pair of setae ; they are small cylindrical processes with rounded extremities, and there 

 are several of them (five or six) upon each side of the body ; occasionally two or more arise from 

 the same base. The setae are strictly paired, and according to LEVINSEN'S figure (1, fig. 5), are 

 exactly like the peculiar setae of Siphonogaster (see below). There is not much information in 

 GRUBE'S paper about the internal characters, but the vascular system seems to be, from what 

 he says, comparable to that of an Oligochaet. The existence of a vascular system at all is, as 

 Dr. EISIG has pointed out *, fatal to a comparison with the Capitellidae ; Alma has been compared 

 by SiMROTH 2 with the Capitellid genus Mastobranchus, to which it certainly bears not a little 

 resemblance ; but neither Mastobranchus nor any other Capitellid possess a vascular system.] 



1 'Die Capitelliden.' Fauna u. Flora dea Golfes von Neapel. 



2 Die Entstehung dor Landthiero: Ein Biologisolier Versuch, Leipsic, 1891, p. 236. 



