62 Proceedings of the Royal Physical Society. 
dimorphic condition of the leaf, how can such specimens as. 
that figured by Germar under the name of Sphenophyllites 
Schlotheimii be explained, where entire and much divided 
leaves occur mixed together in the same individual specimen.’ 
EXPLANATION OF PLATE. 
Sphenophyllum trichomatosum, Stur. 
Figs. 1, 2. From Cooper’s Pit, Worsbro’ Dale, near Barnsley, Yorkshire ; 
natural size. Horizon.—From ‘‘ Rock” over Barnsley Thick Coal. Middle 
Coal-Measures. 
la. Portion of specimen seen on fig. 1, marked a, enlarged, showing 
position of sporangia on bracts. 
2a. Portion of b marked with a * on fig. 2, enlarged two times to show 
small spiney points on outer surface. 
Figs. 3, 4. Portions of leaf whorls; natural size. Horizon.—Shale over 
Barnsley Thick Coal, Barnsley. Middle Coal-Measures. 
VI. On the Pineal Eye of Lamna cornubica, or Porbeagle 
Shark. By G. CaRRincTon Purvis, M.D., B.Sc. Edin. 
[Plate II.] 
(Read 18th March 1891.) 
In the early part of 1890, I received from Professor Ewart 
a small portion of the head-region of an embryo Zamna 
cornubica. The portion included the pineal body, its stalk, 
and the overlying skin. The specimen was not in a very 
good state of preservation for detailed histological investiga- 
tion, yet as embryo Porbeagle sharks are rarely obtainable, 
I was glad to get an opportunity to investigate this portion 
of the head-region as fully as the single specimen would 
enable me to do so. This I did by making a series of longi- 
tudinal vertical sections through the skin and underlying 
tissues of the region made over to me for examination. 
The pineal “ gland,” as it ased to be called, was a prob- 
lematical body to morphologists and embryologists till 1882. 
In that) year Rabl Riickhard? first pointed out that the 
pineal body or “gland” developed in a manner exactly 
1 Vers. d. Steinkf. v. Wettin u. Lobejun, pl. vi., fig. 3. 
2 Archiv f. Anat. und Physiol. (part Anatomie), 1882. 
