I3 THE SCOTTISH NATURALIST 



Sars ' says that the dorsal face is rather convex " and slightly 

 tuberculated," but I have many specimens, from various 

 localities, in which the tubercles are both large and numerous. 

 The lateral cephalic lobes are well developed, terminally 

 rounded, whilst the median lobe is comparatively short and 

 obtusely triangular. The proximal joint of the flagellum of 

 the antenna is slightly shorter than the distal joint. 



P. rathkii possesses many characters that, with little 

 variation, are common to P. ratzeburgii, Brandt, P. pictus, 

 Br., and P. dilatatus, Br., which has led Verhoeff 2 to place 

 all four species in a separate subgenus (Euporcellid). 

 Incidentally it may be remarked that this author's extremely 

 valuable work on the genus Porcellio suffers considerably 

 owing to the lack of figures of his new species, indeed in the 

 entire absence of any illustrations whatever. 



Of the above-mentioned species P. ratlikii is most likely 

 to be confused with forms of P. ratzeburgii and P. pictus. 

 In the former, however, the lateral cephalic lobes are rather 

 large and narrowly rounded at the tip whilst the median lobe 

 is very prominent and almost semicircular. Moreover, the 

 proximal joint of the flagellum of the antenna is about half, 

 or very little more than half the length of the distal joint. 

 In P. pictus the lateral cephalic lobes are very large, and 

 more truncate terminally, as also in P. dilatatus. The 

 median lobe is less prominent and broadly rounded. In 

 both of these latter species the proximal joint of the flagellum 

 of the antenna is the longer, especially so in P. pictus. 



Haplophthalmus danicus, Budde-Lund. This beautiful 

 little species and its near relative H. mengii (Zaddach) are, 

 I feel sure, frequently confused with various species of 

 Trichouiscus, especially the yellow or whitish-coloured forms 

 of T. roscus. Microscopical examination, however, clearly 

 shows that whereas in the members of the genus TricJioniscus 

 the lateral portions of all of the metasomatic segments are 

 clearly visible, in the genus Haplophthalmus only the 3rd, 



1 Crust. Norway, 1898, vol. ii., p. 180. 



2 SB. Gessel. nat. Freunde, 1907, p. 256. 



