Gaily Marine Lahoratort/, St. Andrews. 99 



segment has an irregular border anteriorly', since, besides 

 the two lateral fillets at the cephalic plate, a narrow rira 

 passes in front of the mouth and a broader behind it, the 

 margin of the louver lip being marked by five crenations, the 

 three median and their four grooves being most distinct. 

 Projecting from the mouth are the buccal tentacles, which 

 are smooth. The second segment is narrow-er than tlie fore- 

 going, and has a nearly straight anterior margin dorsally, 

 whilst ventrally it is sinuous, a forward curve in the middle, 

 then a concavity, the lateral border again slightly curving 

 forward. The region containing the foregoing parts forms 

 a blunt cone differentiated from the succeeding, which is 

 wider^ though the maximum transverse diameter is four or 

 five segments behind. 



The branchise are rather massive subulate organs spring- 

 ing from the third, fourth, and the anterior edge of the 

 fifth segment. Each has a short basal region, from which it 

 readily separates, and a tapering distal part ending in a 

 filiform tip. Two are anterior and two posterior. In the 

 smaller examples variation in the origin of the stems exists, 

 the outer anterior being sometimes nearly in a line with the 

 origin of the posterior pair of one side. 



Behind the sixth bristled segment the body gradually 

 diminishes to the tail, which terminates in a median anus 

 with a lateral subulate cirrus on each side. The surface is 

 rounded and smooth dorsally, slightly flattened in front 

 ventrally, and marked by transverse glandular ridges, a 

 distinct median groove running from the middle to the tip 

 of the tail. The length of the body varies from 1 to more 

 than 2 inches. 



The third segment, from its greater width and prominent 

 anterior border, indicates the com mencement of tlie bristJcd 

 legion. Its dorsal margin is boldly concave forward, whilst 

 its ventral edge is nearly straight, and there is little to 

 separate it ventrally from the succeeding segment. It 

 carries on the prominent lateral region the fan-like paleoe, 

 which are more or less horizontal — that is, the concavity of 

 the fan looks upward, the convexity downward, and the 

 longest bristles are internal and their number is from four- 

 teen to twenty. They are flattened golden bristles, minutely 

 striated longitudinally, the striae ending in granules di!?tally, 

 whilst the finely tapered tip is translucent. A few trans- 

 verse bars occur here and there on the shaft, which dilates 

 from the base to the surface of the skin, and then gradually 

 tapers to the attenuate tip. 



The anterior region has seventeen pairs of dorsal bristles^ 



7* 



