tis dM oar iie Mei ism mis 
DR. TRAQUAIR ON THE ASYMMETRY OF THE PLEURONECTIDÆ. 291 
EXPLANATION OF THE PLATES. 
In all the following illustrations, the same numbers apply to the same bones. They are also the same 
as those by which Prof. Owen has distinguished the various bones of the fish’s head in his * Lectures on 
Comparative Anatomy 
1. Basioccipital. 15. Nasal. 29. Articular. 
2. Exoccipital. 16. Petrosal. 30. Angular. 
3. Supraoccipital. 17. Sclerotal. 32. Dentary. 
4. Paroccipital. 19. Turbinal. 34. Preopercular. 
5. Basi-presphenoid. 20. Palatine. 35. Opercular. 
6. Alisphenoid. 21. Maxillary. 36. Subopercular. 
7. Parietal. 29. Inter- or pre-maxillary. 37. Interopercular. 
8. Mastoid. 23. Entopterygoid. 44. Branchiostegal. 
10. Orbitosphenoid. 24, Pterygoid. 50. Suprascapular. 
11. Frontal. 28 a. Epitympanic. 51. Scapula. 
12. Postfrontal. 28 b. Mesotympanic. 52. Coracoid. 
13. Vomer. 28 c. Pretympanic. 72. Supratemporal. 
14. Prefrontal. 28 d. Hypotympanic. 73!. Suborbital. 
PLATE XXIX. 
In all these figures the primordial cartilage is shaded in with horizontal lines. The numbers refer to 
the list already given. 
Figs. 1-7. Illustrations of cranium of Turbot (Rhombus maximus). 
Fig. 1. The cranium seen from above. 
A. The piece of cartilage supporting the four bones of the nasal end of the cranium, and forming the 
anterior part of the septum between the eyes. 
B points to the orbit, bounded on one side by the interocular process (m) of the frontal of the eyeless 
side (11), and on the other by the process (f) of the prefrontal of the same side (14). 
€ c. The two olfactory foramina. 
1l. Frontal bone of the ocular side. 
11. Ditto of the eyeless side. 
14, Prefrontal of the ocular side. 
. M. Ditto of the eyeless side. 
€. À process on each prefrontal, to which the anterior suborbital is attached. 
f. A process of the prefrontal of the eyeless side, sent back to join the process (n) of t = hag 
ing frontal. Thus is the pseudomesial bar formed, and the orbit bounded on the inner side. 
m'. Interocular process of frontal of ocular side. 
- Ditto of eyeless side. 
i. Process on the nasal bone above the apparatus of the jaw. 
k. Process on the nasal bone on which the intermaxillary cartilage glides. 
B. The ridge or spine of the supraoccipital bone, proceeding forwards im the 
little towards the eyeless side. . 
. The dotted line m L represents the direction of the morphological mesial line. 
Fig. 2, Under surface of the same cranium. 
D, Cotyloid cavity for the rounded head of the epitympanic bone. 
pseudomesial line and a 
