On the Development of the Mammalian Phylum. 365 



and three quarter times the lengtli of the combined head and 

 trunk. The head, about half of which is formed by tlie long 

 needle-like beak, is at least twice the length of the trunk 

 proper ; its posterior half is broad, deep, and subquadrangular. 

 Eyes minute, subcutaneous, without any orbital fold. Tiie 

 maxillary teeth are arranged in a single row, and diminish in 

 size but increase in number from behind forwards : the 

 vomerine teeth posteriorly are long and sharp and are disposed 

 in a long, close-set, comb- like series ; anteriorly they form a 

 fine raap-like band : in the mandible a row of large distant 

 needle-like teeth stands up from an uneven band of small 

 denticles. Gill-openings close together, wide. The scaleless 

 integument is thin and deciduous and thickly enveloped in 

 mucus ; no lateral line is apparent. The dorsal fin is feebly 

 developed, and, indeed, hardly distinguishable. The pectoral 

 fin is represented by an inconspicuous clavicular knob, without 

 any rays. 



The abdominal cavity extends at least halfway along the 

 tail. The siphonal stomach, which has its pyloric end long, 

 tapering, and much constricted, leads into a widely expanded 

 duodenum, which, in the single specimen dissected, is fur- 

 nished with a small diverticulum near the pylorus. 



Colour uniform black, with a silvery sheen on the head. 



This species is perhaps identical with Nemichthys infans, 

 Vaillant (nee Glinther), described and figured in Exp^d. 

 Sci. du ' Travailleur ' et du ^ Talisman,' Poiss. pp. 93 and 

 94, pi. vii. fig. 1, and there only doubtfully referred to 

 Dr. Giinther's type. 



EXPLANATION OF PLATE XVIIL 



Fig. 1. Hephthocara simum, sp. n. 

 Fig. 2. Alepocephalus edentulus, sp. n. 

 Fig. S. Xenodermichthys Guentheri, sp. n. 



XLI. — On the Origin and Development of the Mammalian 

 Phylum. By Dr. W. KtiKENTHAL*. 



[An Address delivered on May 28, 1892, in the Aula of the University 

 of Jena, in accordance with the provisions of the Paul von Ritter founda- 

 tion for phylogenetic zoology.] 



Owing to the great division of labour which has taken place 

 in our science, compelling the investigator to occupy himself 

 with individual problems, it is well that we, for once allowing 



* Translated from the ' Biologisches Centralblatt,' xii. Bd. no. 13 

 (loth .July, 1802), pp. 400-413. 



