202 ON PERICIIAETIDAE. 



Perichaeta biserialis Perrier. 

 ( — monocystis Bedd.). 



Some years ago my friend Dr. Th. Lens, Surgeon of 

 our West-India army, kindly forwarded me a bottle with 

 earthworms, collected in Paramaribo. Among them there 

 are several examples , which must be identified with P. 

 biserialis Perr. '), though this species hitherto is not ob- 

 served in South-America , and only mentioned from the 

 distant isles of Madagascar and the Philippines. Like several 

 other earthworms this species therefore appears to have a 

 very wide distribution, probably due to man's interference. 

 According to the investigations of Perrier ^), Beddard ^) 

 and Michaelsen '') P. biserialis is distinguished by the 

 following characters: chaetal ring on a prominent ridge, 

 presenting a ventral gap , on each side of which there is an 

 enlarged bristle , forming thus behind the girdle an apparent 

 longitudinal row of setae on the left and the right of the 

 ventral median line ; upon the segments in front of the 

 girdle, except the anterior ones, two or three setae on 

 each side are thus enlarged. The male generative pores 

 situated on prominent, conical papillae upon segment XVIII 

 and the 3 to 7 succeeding segments each with a pair 

 of copulatory papillae in positions nearly corresponding 

 with them. First dorsal pore in the intersegmental 

 groove XII/XIII. The fifth, sixth and seventh septum are 

 specially thickened; for Beddard's assertion that they 

 should lie one segment more posteriorly 1 think to be 

 erroneous. Two pairs of spermathecae, opening into the 

 intersegmental grooves V/VI and VI/VII, consisting of 

 a globular main pouch , with short excretory duct and 

 a tubular diverticulum, extending over 2/3 of its length. 



i) The collection contained also P. posfAuma Vaill., P. HouUeti Perr., 

 Ponfosc. corethrurus Fr. Mull, and a Benhamia sp. 



2) Compt. Ilendus de I'Acad des Sc. LXXXI, 1875. p. 1043. 



3) Proc. Zool. Soc. 1890, p. 63, pi. IV, fig. 7. 



4) Abhandl. Senckenb. natarf. Gesellsch. Bd. XXI, 1897, p. 226. 



Notes from ttie Leyden UVlu.seu.tn, "Vol. >CX. 



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