152 The Woodlice of the Hull District, 



whose habitat so closely adjoins the sea.' Even such a typical 

 terrestrial form as Porcellio scaher can live for some time under 

 salt water, for Mr. R. S. Bagnall* records a colony of a form 

 of this species living under stones in a marine pool. 



As fc.r as my own observations carry weight, a large pro- 

 portion of the species found owe their distribution in the Hull 

 area to commercial, agricultural and horticultural agencies. I 

 have not found the following species away from the immediate 

 vicinity of houses or gardens : — 



Trichoniscus roseus. Metoponorthtis pruinosus. 



E apinphthalmus danicus. Cylisticus convexns. 



Porcellio loevis. Armadillidium nasaitim. 



P. dilatatus. 



In the paper already referred to, Bagnall holds the opinion 

 that four of the above species, namely, T. roseus, H. danicus, 

 M. pruinosus and C. convexu^j, are truly endemic, but I should 

 be inclined to doubt this myself, judging from my own collecting 

 in the East Riding. It is quite probable that in the course of 

 time introduced species will spread from the ports and other 

 inhabited areas into the open country, and from the usual 

 habitat of the above-named species I should believe this to be 

 more probable than that they had migrated from the open 

 country and found the rich soil of gardens more suited to their 

 needs. This is a question, however, which can only be settled 

 by more extended observations over larger areas, or better by 

 the discovery of subfossil forms, as, for instance, in peat deposits 

 or eld lake beds. 



If a careful search is made in cool greenhouses, in hothouses, 

 and on waste ground near the docks, to the list here given will 

 undoubtedly be added a number of species, such as IJaploph- 

 thalmus mengii, Trichonisc^is pygmceus, Trichoniscoides alhidus 

 and Phihscia patiencei 



The following sixteen species have been found in the East 

 Riding, most of I hem in or near Hull. New records for York- 

 shire are Trichoniscus stehbingi, Porrellio Icsvis and P. ratkei. 

 Including Porcellio raizehuvgii which, though not included in 

 Mr. Rhodes' Yorkshire Tist, is recorded fcr the Scarborough 

 district by Mr. E. A Wallis.f the total number of species 

 recorded for Yorkshire is now 23, abont 65 per cent, cf the 

 total British species. 



Ligia oceanica Linne. 



This fine species occurs everywhere along the Humber 

 shore and many of its tidal affluents, as well as on the sea 

 coast wherever the conditions are suitable. In a paper on 



♦ ' The Woodlice (Terrestrial Isopoda) of Northumberland and Dur- 

 ham," Vale af Derwent, N.H.S. Tvans, 1913, p. 13. 



t See Ann. Rep. Scarb. Phil and Arch. Soc. for 1909. ' Report on the 

 Terrestrial Isopoda 1909/ pp. 23-4. 



Natuva'ist, 



