Gutty Marine Luboralort/, St. Andrews. 103 



the smaller great fang, and the more prominent condition of 

 the crowu with the smaller teeth, four of which are evident 

 as in front. The {^ulur bristles have the same arrangemeiit. 

 The bristles of this region retain the stnieture of tliose in 

 front. As a rule, the luunber of the hooks increases at the 

 fourth segment, and at the sixteenth tliere may be sixteen or 

 seventeen in each row (Anvidsson) . The same author found 

 in an example from Lofoten the tips of the posterior (tenth) 

 bristles feathered with fine lateral hbres, a condition not yet 

 observed here. Arwidsson met with one reproducing the 

 terminal segments without bristles. 



The tube consists of mud and sand-grains round a central 

 lining of amorphous secretion, and is free. It readily yields 

 to jiressure applied externally. Occasionally the translucent 

 secretion projects beyond the external coating of mud and 

 sand. 



In the Irish collection Arwidsson met with Praxillella 

 affinis, Sars, in the form of two mutilated examples dredged 

 otf Mine Head. He found the specially developed capillary 

 bristles on the tenth and eleventh segments. 



The twelfth species, PraxiUella prceteriyiissa, Malmgren, 

 has long been known in the northern parts of Britain, and 

 has a wide distribution elsewhere. The cephalic plate is 

 sloped from above downward and forward, and has a median 

 ridge from its posterior to its anterior border, where it ends 

 in a flattened conical process which curves forward and 

 slightly upward. The rim of the plate has a median notch 

 posteriorly, a deep lateral notch a little more than a ihird of 

 the distance forward, whilst its edge is rounded otf on each 

 side of the anterior median process. The rim in small 

 examples has an entire margin throughout, but in large a 

 scries of notches — about five in number on each side — cut the 

 border between the lateral notch and the median posterior 

 into segments. The deep part of the rim is the anterior 

 section on each side. The nuchal grooves occur on each 

 side of the median ridge, widening a little in their passage 

 forwaid as they run into the notch or angle at the base of the 

 median process. The mouth opens as a transverse slit on 

 the ventral surface a little behind the median process of the 

 cephalic plate, and occasionally the proboscis is extruded as 

 a flattened button covered with small reniform papillae, or in 

 full extrusion as an ovoid sac or bladder. 



The body is of moderate length, more or less rounded 

 throughout, thicker in front and diminished toward the anal 



