1028 -An Interesting Connecting Genus of Chordata. [December, 
There is found, lying in the median orifice of Bothriolepis, a bony 
valve, which is quite free all round. This has been supposed to 
represent the interorbital part of the carapace, and the uncovered 
parts of the orifice, at each of its extremities, have been supposed 
to be the orbits. An examination of numerous specimens of 
Bothriolepis canadensis Whiteaves, has lead me to oppose this lat- 
ter view. I have, on the contrary, considered the entire orifice to 
be probably homologous with the “ nasal pouch ” of the lampreys, 
and the mouth of the Tunicata and of the invertebrates.’ This 
character, together with the absence of lower jaw, would refer the 
genus to the Marsipobranchii or class of lampreys, or to the Tu- 
nicata. From its considerable resemblance in the carapace to the 
tunicate Chelysoma, and in the lateral arms, to Appendicularia, I 
referred Bothriolepis provisionally to that class. 
The Cephalaspididæ are more like fishes than the Pterichthyi- 
dæ, in that they have a distinct head and distinct orbits. They 
have, however, no lower jaw, and thus approach, if they do not 
enter, the Marsipobranchii. But they have no nasal pouch or 
nostrils, as has been observed by Dr. Lankester. This character 
separates them widely from either fishes or Marsipobranchii. It 
also gives color to the supposition that the orbits in this family 
represent the extremities of the median orifice of Bothriolepis. 
A highly interesting specimen, which I owe to the kindness of 
my friend, R. D. Lacoe, of Pittston, Pennsylvania, throws consid- 
erable light on this subject. It consists of the cast of the cranial 
| and nuchal buckler of a vertebrate allied to, but different from, 
— the families above mentioned. The fact that it is derived from 4 
higher geological horizon than any of them, that is, from the. 
} Besides the typical specimen 
buckler are in my possession- 
the fact 
e of Ceph- 
se 
of Bothriolepis. And this median orifice is divided into BE 
al parts by a narrow longitudinal septum. The parts are wee 
e The two mê- 
ifices perforate the middle of the region which is occupied 
