108 STROPHOMENIA SCAXDENS. 



stance escapes high up on the sides of the ventral furrow while the light blue 

 product passes out more ventrally. 



Behind the opening of the anterior pedal gland each side of the foot is 

 accompanied by a longitudinal fold, which persists to near the hinder end of the 

 animal when the lateral ridges, decreasing in size, pass into the general hypo- 

 dermal covering of the body and are covered in large measure by the cuticle in 

 which small spicules may be formed. 



The atrial opening leads into a well-defined cavity (Plate 12, fig. 1) whose 

 walls are provided with organs not unlike those in P. haivaiiensis for example. 

 The outer sensory prominence and the outer and inner ciliated ridges are not so 

 elevated, but the last two are composed of the same type of ciliated cells. At 

 certain points the outer sensory ridge surmounts groups of ganglion cells from 

 which fibres may occasionally be traced into close proximity to nerves that inner- 

 vate the cirri. Along the median dorsal line another well-defined elevation is 

 present between the two limbs of the inner ridge, but its cells are like those of 

 the ordinary buccal epithelium and are probably not highly sensory. 



In cross section the pharynx is roughly semilunar in shape, appearing rela- 

 tively narrow when viewed from the side, but with a diameter of one fourth that 

 of the body when seen from the dorsal or ventral surface. In front of the open- 

 ing of the anterior pedal gland its cells are relatively high and slender, finely 

 granular and contain more or less spindle-shaped nuclei placed at different levels. 

 Behind this point the lining retains the same general character, but is developed 

 into numerous and relatively low transverse folds supported by a small amount of 

 connective tissue. Slightly in front of the labio-buccal ganglia the ridges become 

 higher, the underlying connective tissue more abundant and among the cells of 

 the usual type are a few others of more slender appearance with darkly staining 

 elongated nuclei. It is possible that these elements are sensory in function, but 

 owing to the large quantity of muscle and connective tissue in the neighborhood 

 no special nerve supply has been distinguished. 



Beyond these supposed sensory ridges the digestive tract bends abruptly 

 upon itself and coursing upward and forward unites with the stomach-intestine 

 (Plate 12, fig. 1). There is reason to suppose that this section between the 

 labio-buccal ganglia and the gut represents the oesophagus, but with the excep- 

 tion that its epithelial lining consists of more spongy cells not produced into 

 folds there is little to distinguish it as such. 



The relations of the paired ventral salivary glands (Plate 6, fig. 6) are some- 

 what peculiar and except in very well-preserved material are difficult to determine, 



