14 DALYELLID^.. 



Distigma? helluo, Dies. Syst. Helm. i. 188. 

 Vortex viridis?, Schultze, Nature/. Turbell. 47- 



Hab. Stagnant water. 



Obs. The cocoon is brown and oval, apparent near the posterior 

 end : it contains from four to twelve ova. 



2. D. exigua, ovate-oblong, broadest behind, reddish; eyes black. 

 Length \"'. 



Planaria exigua, Dalyell, Pow. Great, ii. 116. pi. 15. f. 13, 14. 

 Hab. Ponds. 



Obs. When in motion, the form is that of a double cone. 



7. DEROSTOMA. 



Derostoma ( — ), Duges in Ann. ties Sc. not. xxi. 76 (1830). = Oerst. 

 Entw. Plattw. 66 (1844). 



Char. Body linear-oblong, rounded at both ends, with two eyes 



or none : mouth pitcher-shaped, concealed, opening by a longitudinal 



fissure on the venter. 



1 . D. imipnnctatum, plump, narrowed towards the anterior extre- 

 mity, and obtuse behind, dingy yellow ; eyes two, yellow. Length 

 3'"; breadth 1'". 



Derostoma unijnmctatum, Oersted, Entw. Plnttw. 66. tab. 2. f. 25. 

 Turbella unipimctata. Dies. Syst. Helm. i. 225. 



Planaria foflina; — the Quarry Planaria, Dalyell, Pow. Great, ii. 110, 

 pi. 15. f. 7-12. 



Hab. Ponds with a muddy bottom. 



Obs. The specific name is derived from the spot formed by the 

 brown or yellow cocoon in a position behind the mouth. 



2.D. ? vorax, body round, obtuse in front, tapered backwards to a 

 point, greenish; eyes none. Length \\'" ; breadth \'^' . 

 Planaria vorax, Dalyell, Pow. Great, ii. 119. pi. 16. f. 33, 34. 

 Hab. Freshwater marshes. 



Ohs. When gorged with food resembles an inflated vesicle, 

 tapered downwards. The food is seen to fill a capacious ovoidal 

 stomach. There are, in the pregnant mother, from one to five 

 brown cocoons lodged towards the posterior part. 



8. MESOSTOMA*. 



Mesostoma, Oersted, Entw. Plattw, 6"] . 



Mesostomum, Diesing, Syst. Helm. i. 219. Schultze, Naturg. der 

 Turbell. 52. Schmidt, Neue Rhabdocosl. 9. 



* Dnges is the author of the name, and the genus was prohahly founded in 

 1830, not earlier than 1828. Agassiz has not mentioned it, but he has Myozo- 

 stoma of much later creation. 



