SYSTEMATIC 

 ARRANGEMENT OF MAMMALS, 



CLASS XVII. 

 M A M 31 A L I A. 



Vertebrate animals, Lreatliing atmospheric air by lungs; with 

 red, warm blood, heart with two auricles and two ventricles, vivi- 

 parous, lactating, furnished with a muscular diaphragm, covered by 

 skin mostly hairy, armed more rarely with spines, sometimes partly 

 mailed by scutes. 



Section I. Mammalia acotyledona s. implacentalia : JJi/ence- 

 'phala Owen. Uterus double. Placental conjimctiou between 

 mother and embryo none. 



Corpus callosum of brain indistinct. Two marsupial bones in 

 front of symphysis of pubic bones. Four feet in all. 



Order I. Monotremata. 



Cloaca, receiving the outlets of the rectum and the urethro- 

 genital canal. Two clavicles, a coracoid and a furcular. Exter- 

 nal ears none. Teeth corneous or none. Hind feet in males 

 furnished with a perforate sjjur. 



Family I. Monotremata. (Characters of the order those of the 

 single family also.) Feet short, pentadactylous. Snout produced, 

 covered with naked, coriaceous skin. 



Monotremata, from iibuo$ sole, single, and Tprjiia opening, in allusion to 

 the single cloacal aperture for the urinary and intestinal excretions, and 

 for the outlets of the sexual passages. Compare on this order Ducrotat 

 DE Blainville Dissertation sur la place des OniilJwrhynques et cles Echidnes 

 dans les series naturelles, Paris, 1812, 4to, and especially OWEN in ToDD's 

 Cyclopced. in. pp. 366 — 407. 



VOL. II. 39 



