158 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



by the ventral part of the overlying vesicle, the wall of which is closely 

 applied to the smooth dorsal surface of the gland (Plate 1, Fig. 2, par. vs.). 

 The ventral face of the gland is in general convex, but has in it depres- 

 sions which conform to the underlying hard parts of the endophragmal 

 system and shell, and to the muscles upon which the gland rests. The 

 ventral surface differs much in appearance from the smooth dorsal surface. 

 It is uneven, being thrown into numerous ridges and furrows, resembling 

 to some extent the gyri and sulci of the cerebral hemispheres in higher 

 mammals. All these furrows radiate in a general way from a region of 

 the gland lying near the bottom of the hilus, but the individual furrows 

 are comparatively short, and separated by ridges from other furrows in 

 the same radius. The furrow lying in the main axis of the gland is the 

 most prominent and deepest one. It is a direct continuation of the hilus. 

 The dorso-ventral diameter varies, but is greatest in the centre of the 

 organ, and thins out to a translucent edge on the borders. The outline 

 of the border of the gland is irregular. In the middle of the anterior 

 edge there is a sharp V-shaped hilus extending posteriorly 2 to 3 milli- 

 metres (Plate 1, Fig. 1, hi.). The bottom of the hilus marks very nearly 

 the centre of the gland. The median edge of the gland presents a sim- 

 ple curve convex toward the median plane of the body, and having a 

 radius of about a centimetre. The lateral edge is S-shaped, the poste- 

 rior bend of the S giving the gland the appearance of being notched to 

 accommodate the flexor antennarius muscle, on which it does in part 

 rest. This notch is 2.5 or 3 mm. deep and 5 or 6 mm. broad. The 

 edge of the gland for the most of its extent is bluntly toothed or lobed, 

 so that the outline is more or less sinuous. 



For purposes of description the gland proper may be said to present 

 three iobes : a median anterior (lob. m-a., Plate 1, Fig. 1), a lateral 

 anterior (Job. l-a.), and a posterior one {lob. p.). 



The gland measures in its longest diameter, from the edge of the 

 median anterior lobe to the posterior apex, 13 to 15 mm. ; from the 

 bottom of the lateral notch to the middle of the median border, 9 to 

 10 mm. Its greatest dorso-ventral thickness is about 3 mm. It is thus 

 evident that the gland is much flattened. 



In color the gland is a light olive, the ventral face being of a darker 

 shade than the dorsal ; the latter in some individuals approaches yel- 

 lowish brown. The light dorsal surface is surrounded by a narrow 

 border of the darker shade from 1 to 2 mm. in width (Plate 1, Fig. 1, 

 marr/.), which is left without tint in the figure. This border widens to 

 i^uite a broad band on the median anterior lobe. The area of lighter 



