560 PROCEEDINGS OF THE ACADEMY OF [July, 



to'the dorso-median line when the branchiae are spread. They'exhibit 

 the usual irregularity in arrangement, but on the ventral branchiaj all 

 are situated on the proximal ^ and on the dorsal on the proximal!half 

 of the stem, except that on the two dorsalmost they are evenTmore 

 extensively distributed. The ventral stems commonly bear 5 or 6'eyes, 

 occasionally as few as 3, usually distant or in couples. On the dorsal 

 half of the circle of branchise each shaft bears from 7 to 12, even the 

 latter number being exceeded on the dorsalmost pair. Except that 

 they are usually much crowded proximally, they are arranged similarly 

 to the ventral ones. 



As in P. brevihranchiata the collar is intermediate in form between 

 that of Eudisiyla and typical Pseudopotamilla. The dorsal lobes are 

 broadty rounded and slope caudally from their anterior median margin 

 into the dorso-lateral incision ; but they are so largely united with the 

 dorsal'surface of the thorax upon which they rest that only the outer 

 portion is free, though to a greater depth than in P. brevihranchiata . 

 The lateral portions rise abruptly as prominent lobes just dorsal to the 

 collar setae, and then continue of nearly even height until they rise 

 directly into the elongated narrow and pointed ventral lobes. 



Palpal and oral membranes of the usual form are present and the 

 tentacles have a length about equal to the breadth of the thorax, their 

 basal half being broad and foliaceous and the distal half slender and 

 cirriform. 



As a result of having been preserved in the tubes the body is slender, 

 elongated and nearly cylindrical throughout, only a very short region 

 at the posterior end being tapered to the pygidium, while the anterior 

 thoracic region is slightly depressed. Probably as a result of pressure 

 in the tubes, the segments are very faintly separated, except along the 

 glandular ventral plates. Except posteriorly they are rather long, the 

 anterior abdominal and the thoracic ones being from -} to h as long as 

 wide. The pygidium is oblique, with two pairs of minute lobes guard- 

 ing the anus laterally and sometimes a group of numerous small brown 

 specks on each side above. Normally there are 9 thoracic segments, 

 of which 8 are setigerous, though one example has but 7. The abdomi- 

 nal segments vary from 125 on a specimen 60 mm. long to 187 on the 

 largest example, measuring 148 mm. 



All of the ventral plates are narrow, nowhere exceeding ^ the body 

 width and usually much less than this. Corresponding to the form of 

 the segments the extreme posterior ones are 4 times as wide as long; 

 throughout most of the length of the abdomen they are tAvice as wide 

 as long; and those of the anterior abdominal and most of the thoracic 



