NICOLEA LATENS. 431 



The tentacles are all lost, only the slender basal region of a few being present. 



The mouth-opening is large and triangulai- in outline, with the base ventrad. 

 It is bordered by a thick rim which is crossed by numerous deep radial sulci. 

 The peristomium presents below a moderately large lower lip, which is trans- 

 versely elongate and has the anterior margin in general convex, but mesally widely 

 truncate. It is slightly concavely depressed caudad of the anterior border and 

 between the end regions, the depressed region having a length about one half 

 that of the lip as a whole. The depressed area is crossed by numerous longi- 

 tudinal sulci. 



The metastomial somites are convex above and flattened beneath, as usual, 

 with a broad neural depression along the middle in which the intersegmental 

 furrows are deeper and wider than elsewhere. All metastomial thoracic somites 

 are clearly separated by deep furrows ventrally, but only the first five are clearly 

 separated above, the separation between succeeding ones being weak. The first 

 two metastomial somites bulge more convexly ventrally than the others and do 

 not show a neural depression. The first is a little shorter in the midventral 

 region than the labium and shortens conspicuously toward each side; laterally 

 its ventral surface is nearly smooth, but mesally it is crossed longitudinally by a 

 number of deep, closely arranged sulci. Dorsally it is longer than laterally, but 

 shorter than ventrally. The second somite is of nearly uniform length, this 

 being about equal to the median length of the preceding one, the dorsal length 

 being a Uttle greater than the ventral. The midventral region is crossed longi- 

 tudinally by fewer and weaker sulci. On each side, the anterior border is pro- 

 duced forward in a thin lobe which is longest at the dorsal end, where the dorsal 

 edge is straight, and shortens continuously ventrad and gradually disappears. 

 The free margin of this lobe is crenulate, the crenuli small. The third meta- 

 stomial somite is ventrally only about one third as long as the preceding one and 

 widens up the side to the dorsum, the dorsal length being more than twice the 

 ventral. Caudad of the middle above there is a weak transverse sulcus. At 

 the side the anterior border is produced forward somewhat as in the preceding 

 somite, but the thin extended region is shorter. The fourth metastomial somite 

 is, in the midventral region, but little longer than the preceding one. It widens 

 toward and up the sides to the dorsum, where its length is shorter than that of 

 the preceding one. The fifth is ventrally nearly twice as long as the preceding 

 one and is also clearly longer above. The succeeding thoracic somites are more 

 uniform, very gradually increasing in length caudad. Branchiae in the type 

 lost; as shown by the basal elevations and scars, there are two pairs, one each on 



