JutrtJivnrmft of the Vienna Museum. 127 



not Uttered as clitclluni ; ])ut no otlicr structure is sliown in 

 the tlrawiiip^ which could be supposed to bo the clitelluui. 

 And KSchniarda states in the text tliat the clitelluui is usually 

 situated behind. The structure which Schmarda has mistaken 

 ior a clitelluui is really nothing of the kind ; it is formed 

 (fig. 3 a) by a grouj) of segments of a somewhat tumid appear- 

 ance M Inch project beyond the general surface of the body, 

 Fuch as Fritz ]\luller first described* in Urochata corctkrura. 

 This remarkable ];oint of similarity first directed my attention 

 to the probable identity of Pontoscolcx and Urochoila. 



'\ he clitellum, as a matter of fact, is anterior in position. 

 Schniarda noticed that this was the case with some specimens. 

 The error into which he fell is to be accounted for by the fact 

 that in the specimen figured, as in many of those collected by 

 liim, the clitellum was not developed. In those individuals 

 in which it is developed it occupies eight seguients com- 

 mencing with XV. Its extent therefore is precisely that of 

 Urochata, or, as it must now undoubtedly be called, Ponto- 

 scolex coreihrurus. Sclimarda counts seven sette only in each 

 segment, which alternate in position in successive segments 

 from the very first. This enumeration is inaccurate ; there 

 are undoubtedly eight setw per segment on most of the seg- 

 ments ; occasionally on some of the posterior segments of the 

 body I could only find seven, but this is most probably merely 

 due to the loss of one seta. As to the alternation, this only 

 occurs in some of the specimens; perhaps as this fact is the first 

 distinctive point mentioned in the description of the genus I 

 should refer to that genus the individuals which I describe 

 later as Diac/iccia littoralis. As, however, that fact is not 

 referred to in the description of the species, and as the figure 

 seems to me to be a little more like the individuals possessing 

 a clitellum of eight segments, I think that the name " areni- 

 cola " should be applied to them. 



In this species, then, the setas do not alternate froui the very 

 beginning; upon the first few segments (I am not certain 

 how many) they are strictly paired j the two setie of each 

 pair are quite close to each other. In this the species 

 resembles Fontoscolex coreihrurus. But, unlike what is found 

 in that species, the setje are ornamented, as in PJiinodrilus, 

 with a series of curved ridges. In Pontoscolex coreihrurus 

 some of the setai are ornamented, viz. those upon the clitel- 

 lum ; in Ponioscolex arenicola the clitellar are also orna- 

 mented, but they only differ from the sette of the preelitellar 



* " Description of a new Species of Earthworm," Ann. & Mag. Xat. 

 Hist. vol. XX. 1857, p. 13. See also my own observations upon the same 

 btructure in the same journal for January 1891, p. 9o. 



