INTERNAL ANATOMY. 323 
In D. agassizi the palatal spines are entirely solid structures, save at the 
extreme base, where a slight depression exists, so that, while the general external 
form and surface-configuration is very much the same as that in D. hasseltii, 
the internal structure as seen in sections is strikingly different. The presence 
of palatal spines has been indicated in many of the Aplysiidae but in no case 
have any details been given concerning their development or structural rela- 
tions. Bergh (1905, 1907) briefly describes their form and figures them for 
Dolabella rumphii [= scapula], this being the only reference to them in this genus. 
Immediately behind the radula, on the floor of the pharyngeal bulb was found 
a small area of spines similar in form to the palatal ones. They are borne at 
the summit of a transverse crescentic fold, highest in the median line, which 
measures 2.0 mm. in length by slightly more in width. In the unopened tube 
this area would be situated just below the posterior free ends of the palatal folds 
and immediately behind the median groove of the radula. Unfortunately the 
epithelium of this region was somewhat macerated, so that further details 
could not be made out. 
Salivary glands.— The salivary glands have the long strap-shape common 
in the family. They enter the bulb upon the posterior dorsal surface, the duct 
_ continuing forward near the base of the palatal folds, as shown in Plate 9, fig. 7, d, 
and opening into the cavity above the anterior portion of the radula. The pos- 
terior end of the right salivary gland loops across below the oesophagus, its 
tip being attached to the wall of the proventriculus, immediately in front of 
the masticatory stomach. The tip of the left salivary gland is similarly inserted 
upon the opposite side, the relations being the same as in Tethys (MacFarland, 
1909). 
Ocesophagus.— The thick-walled oesophagus, succeeding the pharyngeal 
bulb is relatively short, measuring some 56.0 mm. in total length. At first 
it is large and roomy, ranging in diameter from 12.0 mm. just behind the 
bulb to 17.0 mm. at a distance of 27.0 mm. beyond it. From this point the 
oesophagus rapidly narrows as it passes upward and to the right, reaching its 
minimum diameter of 7.0 mm. just before it suddenly dilates into the pro- 
ventriculus. Its mucous lining is thrown into some ten well-defined longitu- 
dinal folds, from the sides of which numerous minute and short secondary ones 
arise but quickly die away. The main longitudinal folds cease abruptly at 
the entrance of the oesophagus into the first division of the gastric apparatus, 
the proventriculus, or ingluvies. 
Ingluvies and triturating stomach.— The ingluvies is thin-walled and rela- 
