ZOOLOGY. 617 



face iu front of palatines ; " parietal prolonged laterally, not reaching 

 prefrontals; vestibule wall osseous internall}^; liremaxillaries consoli- 

 dated; occipital condyles on cylindrical pedestal, and witli rudimentary 

 limbs. 



II. Proteida Miiller, Cope. Gradients with '"^external gills persis- 

 tent throughout life, maxillaries absent, intermaxillaries and mandible 

 toothed; "palatine and pterygoid bones developed, and orbito-sphenoid 

 elongate and not entering into palate (C). 



3. Proteids. The only existing family with two genera — Proteus and 

 Nechirns. 



III. Trachystomata Miiller, Cope. Gradients with " external gills 

 persistent throughout life; maxillaries absent; intermaxillaries and 

 mandible toothless;" palatines and pterygoids undeveloped, and orbito- 

 sphenoids large, anterior and forming part of i^alate (C). 



4. Sirenids. The only family with two American genera — Siren and 

 Pseudohranchus. 



The transformation of the Mexican Axolotl. 



It has long been recognized that the Mexican Axolotl i^epresented 

 exactly the larval condition of the ISTorth American Amblystomae, but 

 as the Amblystoma form had not been obtained in Mexico, it has been 

 suggested that the Axolotl of that country might never attain the com- 

 plete condition, and that in fact, in its native state, it might exemplify 

 a condition of arrested development perpetuated by its power to propa- 

 gate in an immature stage. A Mexican naturalist has, however, dis- 

 covered that the Amblystoma forui is found and well known arouud the 

 lakes in which the Axolotl occurs, and that it is even known to the 

 peoi)le by a name of Aztec origin meaning land Axolotl. The fully 

 developed form has been found about the lakes Santa Isabel, Xochi- 

 milco, Chalco, and Zumpango, the last of which is about sixteen leagues 

 north of the city of Mexico. Mr. Velasco has recorded his observations 

 in the Mexican periodical called "La Naturaleza," and an abstract is 

 given in the American Naturalist (v. 16, xvi, p. 913). 



Families of Anurans. 



The arrangement of this order was in inextricable confusion till the 

 key was found by Professor Cope, in 1865, iu sternal characters. To 

 the principal of these characters — the manner of connection at the mid- 

 dle — Mr. Boulenger attaches even greater importance than Professor 

 Cope. The order has been i)rimarily divided into two suborders, the 

 Phaneroglossa and the Agiossa, and the former are differentiated into 

 •' sections," the Firmisternia and the Arcifera, the former including the 

 "•suborders" Eaniformia, Firmisternia, and Gastrechmia of Cope, and 

 the latter his suborders Bufoniforraia and Arcifera. Mr. Boulenger's 

 arrangement, so far, appears to be very natural ; but he has paid no 

 further attention to sternal or other anatomical characters to distinguish 



