TRIONYCHID.E. 11 



size ; sculpture coarse and linear ; distal portion of ribs very pro- 

 minent on the under surface of the costals. 

 Hab. Europe (France). 



28904. A costal bone, imperfect proximally ; from the Middle 

 Miocene of Bordeaux (Gironde) France. This specimen 

 accords well with the type costals from the same deposits 

 figured by Delfortrie in the 'Act. ISoc. Linn. Bordeaux,' 

 vol. xxvii. pi. xxviii. figs. 20, 21 ; the extreme prominence 

 of the distal extremity of the rib, well exhibited in 

 fig. 20, is shown very clearly in the present example. 



Purchased, 1853. 



Trionyx, sp. 

 Hab. Europe (England). 



36812 a. The distal extremity of a costal bone ; from the Lower 

 Miocene (Upper Oligocene) of Hempstead, Isle of Wight. 

 The sculpture is fine and linear. 



Presented by S. Laing, Esq., 1862. 



Trionyx gergensi (Meyer l ). 

 Syn. Aspidonectes gergensi, Meyer 2 . 



Imperfectly known. 



The undermentioned specimen apparently indicates a species 

 allied to T. incrassatus (infra), but with the last costals smaller and 

 narrower, and the sculpture on the edges of the costals and nuchal 

 very imperfectly developed. 



The type specimens are from the Miocene of the Mayence basin. 



Hab. Europe (Germany). 



36765. The entire carapace of a large and nearly adult Trionyx, 

 probably belonging to this species ; from the Lower Mio- 

 cene (Middle Oligocene) of Alzey, Hessen-Darmstadt. 

 This specimen is from the same deposits as the type, but 

 in the absence of figures of the latter its specific identity 

 cannot be certainly proved. The strongly-marked spinous 

 processes on the nuchal, noticed in the description of the 

 type, are broken away, but they were evidently originally 



1 Neues Jahrb. 1844, p. 565. — Aspidonectes. 



2 Loo. cit. 



