326 Dr. & the Bev. S. Graham Brade-Biiks on 



is often associated with Cylindromlus sllvarum, and its usual 

 habitat is between the bark and trunk of rotting logs. 



Very few specimens (no adult £), Bakewell district, our- 

 selves, 1918. 



Family Polydesmidae, Leach (ex p.), 1814. 



Genus Polydesmus, Latreille, 1802 & 1801. 



11. P. complanatus (Linne). 



13-28-5 mm. 



This large flat-backed millipede is common in the British 

 Isles. Its gonopods are distinctive. The genus has twenty 

 body-segments. 



*2 c? c? , The Winnats, Gastleton, 7?. S., in a recent year 

 (./.), G. 3149; *2 S 6 and juniors, Cave Dale, 11. S., in a 

 recent year (J.), G. 3136 ; *(J c? ? ? , in a collection from 

 Dove and Mill Dales, R. S., 21/iv./14 (J.); S, "ear the 

 \\. Dove, ourselves, ix./16 ; Bakewell, ourselves, 4/vi./18 ; 

 1 (J, Manners Wood, near Bakewell, W. B. $ 8. G. B.-B., 

 6/vi./18 ; Bakewell distriet, ourselves, 1918. 



12. P. coriaceus, Porat. 



12*5 mm. 



This species is smaller than P. complanatus, also the males 

 have distinctive gonopods. A male from Great Longstone 

 which we dissected for careful diagnosis was 12 5 mm. long. 



Bakewell district, ourselves, 1918. 



13. P. denticulatus, C. L. Koch, 1847. 



10-16 mm. 



Again the gonopods of the male are diagnostic. In this 

 character we did not find the male recorded below quite 

 typical. The slight difference, however, is probably no more 

 than an individual peculiarity in the specimen in question. 

 On the whole the condition of the gonopod is similar to that 

 of the preparation given by Dr. Biolemann in figure 34 in 

 the xviith. paper of the ' Biospeologica ' series (7). In our 

 examp'e the secondary ramus is arched much as that i< in the 

 fig. 34 cited. To adopt the lettering used by Dr. Biolemann, 

 its external appendix ( p) is well developed, broad, slightly 

 arched, and iurnished with a well-marked sharp tooth ( p>) 

 near the base, as in figure 34 (op. cit.). The individual 

 difference we have noted {ante) consists in the presence of a 

 second small tooth on the internal face of the distal part of 



