1886. | LITTLE-K NOWN EARTHWORMS. 299 
Dendrobena, &c.), there have been described more species of Pericheta 
than of any othergenus. Rather more than thirty have been named, 
but several of these, as Dr. Horst’ has pointed out, are merely 
synonyms, while a large number have evidently been too imperfectly 
characterized to admit of recognition. In the majority of cases the 
number of the spermathecze and the absence or presence of variously 
formed diverticula have proved useful as specific characters ; but 
species have been distinguished on other grounds which happen to 
agree in the number and form of the spermathecee. The presence 
of genital papillae is almost universal in the genus Pericheta, and 
these are placed either in the neighbourhood of the spermathecz or 
of the reproductive apertures ; this character serves to differentiate 
P. indica from P. affinis, which otherwise agree pretty closely in 
structure. I have had the opportunity of examining a number of 
specimens of both these species as well as of an apparently new 
species which is closely allied to both. A few notes therefore, which 
will perhaps serve more clearly to define these species, may be worth 
adding to what is known about them. 
Of Pericheta indica I have received about halfa dozen specimens 
from New Caledonia though the kindness of Mr. E. L. Layard, C.M.G. 
The specimens were of varying size, the largest individuals reaching 
a length of some 6 inches. Their colour-(in alcohol) was a very 
dark brown, with an indistinct whitish line in the middle of each 
segment, marking the insertion of the sete. The latter are 
remarkable for the fact that one or more on either side of the ventral 
median line are very much larger than the rest: this fact has already 
been noted by Horst (Nederl. Arch. &c. Joc. cit.), and a similar 
variation in the size of the sete occurs in Perrier’s species P. luzonica 
and P. biserialis*. The two last-mentioned Perichete have up to the 
present been but briefly described ; but the description is sufficient 
to show that they cannot be confounded with P. indica. P. biserialis 
has only two pairs of spermathece and several pairs of genital 
papillee in the segments following the 18th, while there are four pairs 
of spermathecze in P. indica. In P. luzonica the clitellum occupies 
four segments. Dr. Horst mentions two pairs of genital papille 
placed respectively upon segments 7 and 8; in one of my specimens 
there were three pairs, the third pair being upon segment 6. 
Another important variation is in the number of segments which 
compose the clitellum: in most of the individuals where the clitellum 
was developed, it was found to occupy segments 14—16 inclusive, as 
described by Horst for this species and as commonly found in the 
genus. In one specimen, however, the clitellum was a segment 
short, being developed only upon the 14th and 15th rings; the 
clitellum was fully developed upon these segments and sharply 
defined, as it usually is in this genus. It is of some importance to 
note this fact, since a species of Pericheta, P. bicincta, has been 
characterized mainly on account of the restriction of the clitellum 
to two segments. 
' Notes from the Leyden Museum, vol. v. p. 186. 
? Comptes Rendus, t. Ixxxi. (1875) p. 2044. 
20* 
