1870.] MR. J.B. PERRIN ON BALHZNOPTERA ROSTRATA. 807 
animal, which was still further increased by the ribbed arrangement 
of the skin on the anterior half of the ventral aspect. This ribbed 
arrangement was produced by numerous longitudinal furrows or 
sulci, which penetrated fully a quarter of an inch in depth into the 
skin, and ran in a more or less regularly parallel manner from before 
backwards, thus dividing the integument into striz. These striz 
were limited laterally by a line drawn from the angle of reflection of 
the jaws to the base of the flippers, in which situation they were 
short and somewhat arched. The strizee commenced in front at the 
lower jaw, extending its whole length. They were wider both at 
their commencement and at their termination than in the rest of 
their course. The median strize were smaller than the lateral, and 
more uniform in width throughout their entire length, measuring 
about half an inch, and sometimes a little more or less; whereas 
the lateral strie at origin and termination measured from 1} to 
ii inch. Posteriorly they terminated in a radiate manner, those in 
the middle line of the ventral surface being the longest, the remainder 
gradually shortening as they approached the lateral aspect of the 
trunk. The sulci or grooves in the median line presented some 
difference from those more laterally situated. Thus the former 
terminated more gradually than the latter, and resembled a cut made 
into the skin by an inexperienced operator; the lateral sulci termi- 
nated sharp and abruptly. These plicze or folds did not decussate, 
or decrease in number in their transit from before backwards, as 
mentioned in Carte and Macalister’s specimen ; they were continuous 
and well marked throughout. The sulci were wedge-shaped, and 
not quadrilateral as shown diagrammatically by Hunter; no doubt, 
if the integument were considerably distended they would present 
that appearance. 
The flipper was traversed about the middle of its entire cireum- 
ference by a zone of white, which contrasted strongly with the slaty 
black which extended along its basal extremity for about eight inches, 
and for the same distance along its distal end. This white zone at 
the basal end was limited by a sharp and abrupt line of termination 
directed obliquely from before backwards. Distally it terminated in 
a radiate manner, the white becoming gradually lost in the black. 
The ventral surface of the tail was likewise covered with white 
integument, except at the margins, where the white and black gra- 
dually merged into each other. 
The Cranio-mandibular Articulation.—This articulation presented 
several remarkable and interesting features. It was effected by 
means of a huge fibro-elastic mass, spheroidal in shape and closely 
adherent by both of its extremities to the squamosal posteriorly, 
and the condyle of the mandible anteriorly. A small portion, how- 
ever, of the concavity of the squamosal was free, the cartilage being 
unattached, as ascertained by making an artificial opening ; the finger 
could be readily passed for a short distance underneath. There 
was not the slightest trace of a synovial membrane even here; and 
the close adherence of the elastic mass to the rest of the squamosal, 
on the one hand, and the globular head of the mandibular arch on 
Proc. Zooxu. Soc.—1870, No, LIV. 
