THE GKNKRA A.ND SPECIES OF SYJJ PHYLA. 15 



conspicuously lougei*, and scarcely ever shorter than the 

 other. The anterior is inserted on the distal end of the 

 " prjBtarsus/' the other claw on the posterior side of the same 

 joint ; the morphological interpretation of the prsetarsus and 

 the two claws is that set forth on similar parts in Japyx 

 solifugns, in § 51 of my paper '^Zur Morphologic der 

 Gliedmassen und Mundtheile bei Crustaceen und Insekten^' 

 (^Zool. Anzeiger/ 1893, Nos. 420 u. 421). 



The last pair of the legs mentioned present the specific 

 characters especially well developed ; the penultimate and 

 antepenultimate pairs can also be used. The length of the 

 tarsus in proportion to its depth, and the number and length 

 of outstanding dorsal setee both on this joint and on the 

 metatarsus and tibia, present good characters in Scolopen- 

 drella. In Scutigerella the shape of the tarsus is of lesser 

 value, as it sometimes shows variation between large and small 

 specimens, etc. (see above, and also under the descriptions 

 of the species) ; the number and the length of the setae in the 

 anterior dorsal row on metatarsus and tarsus and the length 

 of a distal seta on the tibia are always valuable, though some- 

 times also presenting variation to a certain degree. The 

 claws of the posterior pairs are important in Scutigerella, but 

 must be studied with caution, as an oblique position of one of 

 the claws under the microscope easily conveys a misleading 

 image. In Scolopendrella the claws are less valuable, their 

 difference in various species being generally smaller. It 

 should be emphasised that the last pair of legs must be fully 

 developed, at least quite as large as the preceding pair, and 

 with the number of seta3 at least as high as on those legs, 

 otherwise the shape of their tarsi and claws and the number 

 of their dorsal setas will give misleading results. 



Various names have been given to the well-known 

 moveable, protruding organs at the base of each leg of the 

 ten posterior pairs; I will name them exopods, but must 

 abstain from setting forth here an explanation for the choice 

 of this name. These exopods are very short and difficult to 

 discover in all species of Scolopendrella and in Scutigerella 



