134 MR. E. PIIKLrS ALLIS, JUN., OX 



and as directly continuous with it, the processes thus being of 

 trabecular origin. Schauinsland says that these processes support 

 the rostrum. Garman (1904, p. 252) says there is no rostrum in 

 these fishes, but the presence of the rostral processes suggests 

 that a rostrum existed in ancestral forms and has become ob- 

 solete. Gegenbaur (1898) says that the three rostral processes 

 correspond to, but are not directly descended from, the three- 

 limbed rostral basket of the Oarchariidje and Scylliidse, this 

 implying that they are directly continuous with the cartilage of 

 the chondrocranium. Dean (1906) shows the median process 

 directly continuous with the cranial cartilage in a six- month 

 embryo of Chimara colliei, but says {I.e. p. 129) that: "I am 

 inclined to interpret it as an element, /. e., a fin support, trans- 

 posed from a hinder position," which would mean that it was not 

 primarily a part of the cranial cartilage. The lateral I'ostral 

 processes he says are " later developed into long and separately 

 jointed elements." He considers the median bar of the rostral 

 basket of the Carchariidse and Scylliidae to be probably represented 

 in the septal plate of Schauinsland's descriptions of Callorhynchus, 

 and hence not in the median rosti-al process of that author's 

 descrijjtions. The lateral bars of the rostral basket of the 

 Selachii are said to be possibly the homologues of the little 

 processes s of Schauinsland's descriptions of Cullorhynchus, to be 

 later considered. 



In my specimens of Chimcera colliei, I find the median rostral 

 process articulating with and strongly bound by ligamentous 

 tissue to, but not directly continuous with, a slight eminence 

 of the chondrocranium that lies on its dorsal surface between 

 the two anterior openings of the ethmoidal canal. The lateral 

 process of either side arises from a thin and flexible portion of 

 the anterior edge of the dorsal wall of the nasal capsule, and it is 

 apparently directly continuous with the cartilage of that wall, 

 the sui'faces, when the process is removed, always appearing 

 fractured. The median process runs at first dorso-anteriorly and 

 then turns somewhat abruptly ventro-anteriorly, and extends ap- 

 proximately to the level of the outer ends of the lateral processes. 

 From about the middle of the length of the proximal portion of 

 the median process a ligament arises and runs antero-ventrally in 

 the median line until it reaches the level of the lateral processes. 

 There it spreads dorsally, ventrally and laterally and is lost in 

 a layer of tough fibrous tissue that lies internal to the latei'O- 

 sensory canals on the ventro-anterior sui'face of the snout, and 

 forms part of the fibrous layer of the corinm, to be later described 

 in connection with the ampuUary tubules. A stout ligament, 

 which extends mesially from the outer end of each of the latend 

 processes, also lies in this tough tissue, and is thus indirectly con- 

 nected with the median ligament just above described as well 

 as with its fellow of the opposite side. Gegenbaur (1898) found 

 these three ligaments represented by cartilage in one specimen 

 of Chiino'ra, the ligaments of my specimen thus being capable of 



