DAVIS : NOTE ON CHLAMYDOSELACHUS. 
105 
Possibly the bases of C. mirahilis might not accord so well. 
Pternodus springeri and P, armatus ( Pristicladodus springeri and var. 
armatus, St. J. and W. ) present forms of bases which are intermediate 
between those of Chlamydoselachus and Cladodus, as shewn in the 
numerous specimens figured by St. John and Worthen." 
The scales on the entire body are small ; and irregular in size 
and shape. On the sides and abdominal surfaces the3'' are depressed 
polygonal plates surmounted by one, two, or three sharp prominences, 
the median of which is the stronger, in places becoming a keel. On 
the tail this keel is produced beyond the base as a sharp spine with 
thin longitudinal ridges. About the mouth and in particular around 
its angles, the spines are larger, more conical and more erect ; more 
like teeth. In the mouth, just behind the last row of teeth, there 
are spines, which are more slender^ and which have broader bases ; 
these resemble the teeth of certain fossil species which have single 
cusps. They are hardly one-fourth as large as the teeth immediately 
it front of them. Where worn the scales are smoother. The upper 
edge of the tail and its posterior border, to the lateral line, is armed 
with a sharp edge of scales. The edge is formed of two rows, one 
from each side, of broad thin, subquadrangular scales which have 
met on the median line and become so closely applied as to appear a 
single ridge. Near the base the plates ai-e striated : the distal 
halves are smooth. Similar scales guard the front or upper edge of 
the dorsal fin : aud on each side of the lateral line, elongate scales 
with truncated ends protect the canal. 
The internal organization of Chlamydoselachus offers quite as 
many peculiar features as its external. The head is comparatively 
small for the length of the body ; the jaws are long compared with 
the head, and are suspended considerably further back than in any 
existing shark, and present a remote resemblance to the serpents. 
In the Notidanidse the articulations of the jaws are as far back as in 
any of the sharks, but even in that family the jaws pass a little 
behind the skull, whilst in this genus they extend nearly as far 
behind the occipital as in front of it. Mr. Garman remarks that 
" the skull of the frilled sharks is suggestive of immaturity : the 
thin walls, soft cartilage, and large pores and foramina Avith thin 
