Miscellaneous. 73 



developed; respiration is entirely effected by highly specialized 

 lungs commuraicating with a common trachea ; and the lower jaw is 

 composed of simple rami, and articulated directly with the skull, the 

 OS quadratum of the other vertebrates being converted into one of the 

 auditory ossicles (the malleus). This superclass is represented by a 

 single class — the Mammals. 



The more these groups are studied in all their relations, the more 

 natural do they appear. 



As to other questions — that is, whether the true Fishes and 

 Selachians are not separate classes, there is much to be said on both 

 sides, and i)erhaps the arguments in favour of the class value of the 

 Selachians may be even more weighty than those against them. If, 

 indeed, the Birds and Reptiles are differentiated as distinct classes, 

 similar rank can scarcely be consistently withheld from the Fishes 

 and Elasmobranchiates. If I have heretofore hesitated, it is becausi' 

 of Dr. Giinther's very adverse views. 



Without prejudice to the reconsideration of the question as to the 

 systematic value of the group of Selachians or Elasmobranchiates, 

 the classes of vertebrates may then be distributed, in a descending 

 series, as follows : — 



Branch VEBTEBRATA. 



A. Subbranch CRAMOTA. 



Superclass Malleifera. 



I. Class Mammalia. 

 Superclass Quadratifera. 



(Sauropsida.) 



II. Class Aves. 



III. Class Reptilia. 

 (Batrachopsida.) 



IT. Class Batrachia. 

 Superclass Lykifera. 

 V. Class Pisces. 

 YI. Class Elasmobranchiata. 

 Superclass Monorruina. 



VII. Class Marsipobranchia. 



B. Subbranch ACRANIA. 



VIII. Class Leptocardia. 



The most nearly related pair of classes are those of Birds and 

 Reptiles ; and preeminently the most homogeneous is that of Birds, 

 all the living representatives of which seem to be members of a 

 single order (which may be distinguished by the name Eurhipidura), 

 and at most divisible into two suborders, the Carinata) and the 

 Ratitai. Other orders are represented by extinct tj-pes, viz. Saururte 

 and (if the vertebra? are peculiar to the group) Odontornithes. — 

 Abstract of a communication to the National Academy of Scienr.s, 

 made Oct. 29, 1873. Communicated by the Author. 



Ann. c& Mag. N. Hist. Ser. 4. Vol. xiii. 6 



