Baur.] -^lO play 5, 



the study of difFerent skulls I have found that this species Aspidonectea 

 has to be associated with Trionyx triunguis, T. sinensis, T. calif or nianas, 

 T. sinnhoei and 2\ euphraticus. 



The following generic names have been applied to these forms since 

 Fitzinger, in 183(5, besides the many names given by Heude : 



Pelodiscus Fitzinger, 1836 (2'. sinensis Wiegm., T. labiatus Bell), =; 

 Ami/da Fitz., 1836 (7'. euphraticus, 2\ triunguis). 

 Tyrse Gray, 1844 {T- triunguis, T. sinensis, T. euphraticus). 

 liiifetus Gray, 1864 (2\ euphraticus). 

 Landeinania Gray, 1869 (?'. sinensis). 

 Fordia Gray, 1869 (2'. triunguis). 

 Fotamocheli/s Gray, 1870 (2". sinensis). 

 Oscaria Gray, 1873 (2'. swinhoei). 



Of all these, Pelodiscus is the oldest, and I shall therefore introduce it 

 again. 



Pelodiscus Fitzinger (name only). 



Posterior nares reduced in size by the inner and posterior extension of 

 the maxillaries. Alveolar surface of lower jaw without longitudinal 

 symphyseal ridge ; seven to eight pairs of pleuralia, last pair in contact in 

 the median line ; a single neural between the first pair of pleurals. 



Type, Aspidoneetes sinensis, Wiegm. 



Other species : P. triunguis Forsk. 

 P. swinhonis Gray. 

 P. euphraticus Daud. 

 P. agassizii Baur. 

 P. calif or nianus Rivers. 

 The genus Amyda Fitz. contains the three species Trionyx cartilaginew, 

 T. muticus and T. euphraticus. Of these, 2'. euphraticus has already 

 been placed in Pelodiscus. 



The Trionyx cartilagineus was placed in a special genus by Gray, with 

 the name Dogania, in 1844. Trionyx muticus was kept in Amyda by 

 Agassiz, in 1857. Both these genera have to be retained, each with ji 

 single species. 



Dogania Gray, 1844. 



Posterior nares reduced in size by the inner extension of the maxilla- 

 ries. Alveolar surface of lower jaw without a longitudinal symphyseal 

 ridge ; eight pairs of pleuralia, all separated by neurals ; a single neural 

 between the first pair of pleurals. 



Type, Trionyx subj)lanus GeofFr. 



Amyda Fitzinger, 1836 (name only), Agassiz, 1857. 

 Posterior nares not reduced in size by the inner extension of the max- 

 illaries. Alveolar surface of lower jaw without a longitudinal symphys- 



