1886. | ON SQUALORAJA POLYSPONDYLA. 527 
body (Plate LIT. fig. 1) in a later stage. Lettering as in last 
plate. 
Fig. 7, 8. Orranees sections through a portion of outer surface of multicel- 
lular body in a later stage. a, degenerating nuclei ; other lettering 
as before. 
9. Multicellular body from.ovum of Protopterus, differing from that 
illustrated in fig. 1 mainly by the absence of follicular layer. 
Lettering as before. 
10. Portion of secondary follicular layer at point marked with an arrow 
in preceding figure; more highly magnified. 
11. Central mass of a body belonging to same stage as that figured in fig. 9, 
to show the mass (p) formed by the breaking down of the central 
cells (c), the nuclei of which (7) are here and there imbedded in it. 
12. One of central cells (Plate LII. fig. 1,c) with a large number of 
nuclei. 
13. Three central cells from Stage I. (fig. 1, 4), to show difference in 
nuclei. 
14-20. Central cells very much enlarged from Plate LIT. fig. 1, to show 
the different stages in degeneration of nuclei. 
21. Nest of germinal cells in ovary of Ceratodus at a later stage than that 
in Plate LII. fig. 3. Lettering as in that figure. 
Puate LIV. 
Fig. 22. A portion of body represented in Plate LIIT. fig. 21, more highly 
magnified. Lettering as in fig. 21. 
23. Nest of germinal cells in ovary of Ceratodus at a stage near to that 
represented in figs. 21 and 22. Lettering as in those figures. 
24, Portion of multicellular body in ovary of Protopterus, to show masses 
of yolk (a), apparently corresponding to areas occupied by fused 
masses of protoplasm in earlier stages (p in figs. 1, 9, and 11). 
25. Multicellular body of Ceratodus at a stage corresponding to that of 
Protopterus, illustrated in fig. 1. a, fibrous tissue of stroma-layer ; 
other lettering as in fig. 1. 
26. A portion of central cells of multicellular body of Ceratodus, more 
highly magnified. Lettering as in fig. 1. 
27-31. Central cells of multicellular body of Protopterus at an early stage, 
to show commencing yolk. 
32, 33. Central cells of ditto, to show disintegrating nucleus, 
2. On the Anatomy and Systematic Position of the Liassic 
Selachian, Sqgualoraja polyspondyla, Agassiz. By A. 
Smith Woopwarp, F.G.S., of the British Museum 
(Natural History). 
[Received October 18, 1886.] 
(Plate LV.) 
’SuMMARY OF Previous RESEARCHES. 
The prolific fish-beds of the Liassic formation have yielded so 
much valuable material during recent years, that it is now possible 
to considerably supplement the original anatomical memoirs of 
Agassiz, Egerton, and the other pioneers in early Mesozoic ichthy- 
ology. Many specific types that were at first only known from very 
