272 V. L in stow: 



the mucous membrane, that they broke across when pul- 

 led ; and some even remained adherent after having been 

 placed in spirits of wine. They are the largest specics 

 of Trichosoma which I have scen, the posterior division 

 of the body in some being so thick as in a certain degree 

 to resembie this part in the Trichocephalus, from which, 

 however, they are readily distinguished, the increase 

 in diameter being gradual, and not sudden. They 

 are about 8 lines in length, the body white and cylin- 

 drical, the posterior extremity rounded; in the thicker 

 part of the body the alimentary canal appears to be some 

 what Spiral, and is surrounded by the convoluted ovaries. 

 All the specimens -which I have appear to be females. 

 This species has not, I believe, hitherto been described, 

 although it is very common, and I have frequently raet 

 with it. It occurs in the urinary bladder, both of the 

 male and female rat, and is quite distinct from the spe- 

 cies which inhabits the small intestine of the same animal. 



From the thickness of the posterior part of the body 

 compared with other species of Trichosoma, 1 would ven- 

 ture to suggest for this species the name Trichosoma 

 crassicauda. 



Ray er giebt an ^): 



Trichosoma muris deoumam. 



J'ai rencontrö fr^quemment ces vers, pendant les mois 

 de novembre, decembre 1842, et janvier 1843, dans la 

 vessie des surmulots, surtout chez ceux qui provenaient 

 des environs des clos d'equarrissage, On trouve aussi 

 plus frequemment les vers chez les vieux surmulots que 

 chez les jeunes- Je n'en ai point observ^ chez le rat 

 noir (mus rattus), qui est beaucaup plus rare, h Paris, et 

 qu'il est plus difficile de se procurer. Cependant, j*ai 

 disseque ce rat un nombre de fois süffisant pour en inf^rer 

 que, si ces vers existent quelquefois dans cette esp^ce, 

 ils doivent y etre rares. Pour donner une idöe de leur 

 frequence chez le surmulot, il me suffira de dire, qu'il 



1) Archives de Medecine comparee I, 1843, pag. 180—182, 

 pl. XII, Fig. 12—19. 



