252 RKCOIIDS OF THE AUSTRALIAN' MUSEUM. 



The wonns, toi), were soft and so readilv torn iu liaiidling that 

 it was not possible to make satisfactory dissections for the isohition 

 ■of the genital ducts. Sections have been prei)ared, which with 

 the study of entire intlividuals, both in glycerine, and after being 

 stained, have enabled me to give the following account. 



Of the three species, Tnhif'e.v davidis is readily distinguishable 

 by its larger size, especially by its greater stoutness ; the other 

 two are moi'e slender and scarcely distinguishable from one another 

 except by aid of the microscope, though Fhrfodriluide!< Jiotahi/is 

 is altogether a more delicate worm than Brdin'hinra lAenrotheai. 



I have not attempted to make .an exhaustive study of either 

 species, but have limited myself to a description of such features 

 ■as are important in characterising the species. 



The types and microscopic preparations which wei'e used in 

 this study, are in the Australian Museum. 



TUBIFEX DAVIDIS, .s;^. nov. 



(PI. xlvi., Hgs. 1-6). 



The numerous individuals of this worm seem to indicate that it 

 is the predominant species, so far as this collection allows me to 

 judge. Unfortunately the majority are broken, and others so 

 i-oiled as to make it impossible to give reliable measui'ements. 



Dimensiofis. — I estimate that the worm measures from 25 to 

 40 mm. in length, with a diameter of 1 mm. 



The skin is smooth, there are no papillae, though the j^osterior 

 segments are highly glandulai-. 



The Protttondn/in is bluntly conical, and is etjual to nearly twice 

 the length of the first segment. 



Choitfe. — The usual four bundles are present on each segment ; 

 the dorsal bundle consists of two kinds, "capilliform" and "forked 

 •crochets," but in the anterior dozen or so segments some of the 

 latter have an extremely delicate membrane, or a single inter- 

 mediate tooth, between the limbs of the fork ("ctenates") (PI. 

 xlvi., fig. 2). 



The two kinds of cluetaj alternate in a bundle, and in tlie 

 greater part of the worm each bundle consists of three or four 

 ■capilliforms and three or four crochets ; but in the ante-clitellian 

 segments, the number of capilliforms is increased to six or even 

 seven — in these segments the additional capilliforms are dorsally 

 placed (PL xlvi., fig. 1). 



