362 



PROF. W. N. PARKER ON THE 



[June 19, 



In both species distinct glands are present in the grooves of the 

 opercular and dorsal spines, and in the former they are very large, 

 extending a considerable distance both above and below the spine, 

 along the greater part of its length. The glands consist of rela- 

 tively enormous granular nucleated cells, the structure of which is 

 apparently similar in both species. 



Plate XVII. fig. 1, taken from a transparent preparation, shows the 

 general form and relations of the opercular glands. Anteriorly both 

 dorsal and ventral portions project into the bony cavities already de- 

 scribed as being present at the junction of spine and bony operculum. 

 From this region each gland broadens out to form a large anterior 



Fig. 1 



Fig. 2. 



a'r 



TracMnus draco. 



Fig. 1. External view of the left opercular bone and its spine. 

 Fig. 2. Side view of the third dorsal spine. 



ar. Articulation of opercular bone with hyomandibular. gr. Groove in spine. 

 op. Opercular bone. op.s. Opercular spine. z. Conical cavities in 

 opercular bone, continuous with the grooves of the spine. 



lobe, which in its widest pai t consists roughly of about nine or ten 

 irregular rows of cells. About halfway along the spine the anterior 

 lobe gradually narrows, and ends a short distance from the pro- 

 jecting apex of the spine. 



In Plate XVII. fig. 2 a surface view of the apex of the spine is 

 shown, indicating the manner in which it usually projects from its 



