336 Dr. O'Bryen Bellingluun on Irish Eatozoa. 



This genus was established by Schrank under the name Fes- 

 tucaria, changed to Monostoma by Zeder, and adopted by Ru- 

 dolphi and all zoologists since. 



The species are not numerous : Rudolphi enumerates thirty 

 species, of which seven are doubtful. They are most numerous 

 in birds and fish, less common in reptiles, and are very rare in 

 mammalia. They inhabit the alimentary canal principally ; a few 

 have been detected in the abdominal cavity and in the lungs. 



The species are arranged by Rudolphi in two sections, accord- 

 ing to the situation of the anterior solitary pore. Those included 

 in the first section have the orifice of the pore inferior, occur only 

 in fish, and have been by some classed together under the name 

 Hypostoma. The few species in this list belong to the second 

 section, in which the orifice of the pore is anterior. 



Pori apertura antica. 



rCseca of shieldrake {Tadorna Bellonii). 



,_ , ^^ ^ -k J Cseca of widffeon (Mareca Penelope). 



1 , Monostoma attenuatum *<ri riu- t ^ lu- 



1 Caeca of laughmg-goose {Anser albt- 



y_ frons) . 



rCseca of pochard (^Fuliyula ferina^ . 



j Caeca of shoveller (^Anas Clypeata). 



2. . verrucosum^ ^ Cseca of water-hen (GaZ/mw/a chloro- 



I pus). 



[_C3eca of bald-coot (Fulica atra). 



* The Monostoma attenuatum was discovered by Rudolphi in the 

 caeca of the snipe ; he mentions the caeca of the shoveller duck as 

 another habitat. I have obtained it from three other species ; it oc- 

 curred in greatest abundance in the shieldrake. This and the next 

 species appear to be altogether confined to the caeca of birds. 



The Monostoma attenuatum is a minute species, measuring only a 

 line and a half in length ; the colour is whitish, with a shade of yel- 

 lowish red. The body is slender, flattened and smooth, obtuse and 

 rounded posteriorly, becoming more slender anteriorly ; the pore is 

 anterior, terminal, orbicular and slightly prominent. The ovaries are 

 situated in the posterior half of the body. From the anterior pore 

 two white lines (apparently vessels) are seen to run backwards ; they 

 are obscured when they meet the ovaries, but posteriorly they are 

 again seen, and can be traced to the posterior extremity. 



f The Monostoma verrucosum has been named so from the little 

 tubercular prominences with which the body is provided ; these are 

 seen only upon one surface, and Rudolphi calls it the abdominal sur- 

 face ; it appears to me to be the dorsal surface of the animal ; it is in 

 general convex. I have found this species upon two occasions in 

 considerable numbers in the caeca of the common shoveller {Anas 

 Clypeata) ; they are about a line in length, and about a third of a line 

 in breadth, of a reddish yellow colour. When placed in water they 



