PACHYMENIA ABYSSORUM. 73 



surface possibly enabling the animal to crawl about on the bottom ooze. As in 

 the case of Alexandromenia this individual is unattached and may be accord- 

 ingly a roving form. 



The cuticle is approximately three times the thickness of the hypodermis, 

 but is scant in amount owing to the vast numbers of needle-like spicules, of 

 varying sizes, imbedded in it. As noted above the hypodcrmal layer is not in a 

 good state of preservation, but it may readily be discovered that the cells are 

 unusually slender, and laterally and ventrally form papillae in the head region. 

 There are low elevations at other points over the body but it is not certain that 

 they are definite papillae. 



The external opening of the anterior pedal gland is a cavity of large size 

 whose walls are provided with folds of unusual height. On the posterior wall 

 these are approximately seven in number, the outermost on each side being 

 very large. Behind the cavity the five included folds disappear while the large 

 lateral ones unite in the formation of a foot with a creeping surface of greater 

 width than in any other known species of Solenogastre. In the posterior end 

 of the body the foot decreases in size and becomes continuous with small folds 

 of the cloacal wall. 



The anterior pedal gland is a voluminous organ lying at the sides of the 

 body opposite the external outlet. The cells composing it are exceptionally 

 small but otherwise present no noteworthy characters. Behind it shades into 

 the posterior pedal gland without any appreciable change in the character of the 

 cells. Throughout the entire extent of the foot the gland is unusually large 

 and the ductules appear to open over the entire creeping surface. 



The external atrial opening is subterminal and large, and leads into the 

 customary cavity provided with ridges and cirri typically situated. As may be 

 seen in Plate 39, fig. 1, the external ridge is continuous across the mid line in 

 front of the external opening of the atrium and though relatively small at this 

 point it rapidly increases in height, finally becoming of such a size that it may 

 be seen in external view. The inner ridge is likewise small anteriorly but behind 

 becomes as extensive as the external fold. Behind these two folds are con- 

 tinuous with each other and are connected with several long plaits in the hypo- 

 dermis which extend to the external opening of the pedal gland. The cirri are 

 simple unbranched processes, slightly pigmented and contain a muscle or nerve 

 fibre extending, in some cases at least, throughout their entire extent. 



The atrium communicates dorsally with the succeeding section of the 

 digestive tract whose general relations may be determined from an examination 



