On a remarkable kind of Air-bladder. 349 



under surface of the intestinal tract greatly increase in size at 

 the junction of the abdomen with the cephalothorax. In 

 males and females without ova the exterior of the gut is 

 sparingly supplied with such tissue. 



This crab affords a good example of the " commensalisme " 

 of Prof, van Beneden. Nemertes carcinophila abounds on 

 the hairs bearing ova ; and the young of the common mussel 

 and other adventitious growths are common, besides Sacculina ; 

 Trematode larvse in the liver and other parts. Various abnor- 

 malities from injury also occur. The colours of the males are 

 often remarkably bright, both on the upper and under surfaces 

 of the carapace. 



Fam. Corystidse. 

 Genus Atelecyclus, Leach. 

 Atelecyclus septemdentatus , Mont. ; Bell, op. cit. p. 153. 

 Frequent in the stomachs of cod. 



Genus Corystes, Latreille. 

 Corystes cassivelaunus, Penn. ; Bell, op. cit. p. J 59. 

 Common on the West Sands after severe storms. 



Fam. Pinnotheridse. 

 Genus Pinnotheres, Latreille. 

 Pinnotheres pisum, L. 5 Bell, op. cit. p. 121. 

 Frequent in Mytilus modiolus. 



[To be continued.] 



XLI. — Description of a remarkable kind of Air-bladder. 

 By Dr. Albert Gunther, F.R.S. 



[Plate XVIII.] 



Among the specimens of mollusks purchased by the Trustees 

 of the British Museum from the Collection of the late Dr. 

 van Lidth de Jeude there was a preparation, which, on closer 

 inspection, proved to be the air-bladder of a fish. Although 

 there was no indication as regards its origin, I have no doubt 

 that the species from which it had been taken belonged to the 

 Scisenidas, a family distinguished by the singular structure of 

 that organ. In some degree the present specimen resembles 

 Ann. & May. N. Hist. Ser. 4. Vol xiv. 25 



