Gdtty ^[arine Labor alor y ^ St. Andrcicn. 41 



a Ijii d's head. Above tlic main fang tlic ronnded crown lias a 

 scrirs of ronr smaller teeth. This kind of hook is charac- 

 teristic of the bristle-bearing segments. 



A seri(S of vertically tialtencd uneinigerons l;imellno orcnr 

 on the succeeding segments, and some are broader at tlic tip 

 than tlic base. They bear at their apices a row of minute 

 avicular hooks, having short, broad, basal processes with a 

 convex inferior outline, a j)osterior outline in which a deep 

 sinus occurs above the basal j)rocess, and an anterior outline 

 which in some has a trace of a ])roce.ss beneath the main 

 tooth. The latter is of moderate size, but the teeth above 

 it are proportionally large, so that this hook docs not 

 present the disproportion between the first and succeeding 

 teeth present in the long anterior hooks. In lateral view 

 four or five teeth occur above the great fang, and in reality 

 they form a rounded crown with their points curved oljliquely 

 downward. Mahngren, while noting the distribution of the 

 hooks from front to rear, does not suiheiently define the 

 structure of the posterior hooks. 



As widely distributed is the twenty-fifth species, Tere- 

 hcUides strotmi, Sars, in which tlie cephalic region is almost 

 as blunt as in Tricliobraiichits, though the great elevation of 

 the frilled cephalic plate is characteristic, since it rises Irom 

 a slight collar liigh above the (lorsal outline and has a boldly 

 folded margin, the two sides meeting in the middle line 

 inferiorly, and forming a spout-shaped channel, the sides of 

 which behind the mouth in some are thickened. The cephalic 

 ])late thus has the surfaces directed anteriorly and posteriorly, 

 instead of dorsally and ventral ly as in I'ulycirrus and other 

 forms. The edges of the plate posteriorly give origin to 

 the tentacles, which are of a pale flesh-colour, grooved, often 

 spoon-shaped, and, though not stretching much, coil actively 

 in every direction. 



The body is enlarged in front and gently tapers to the 

 tail, which is by no means slender. It is smoothly rounded 

 on the dorsum and only in well-preserved examples are the 

 lines of the segments indicated. On the other hand, the 

 ventral surface presents anteriorly the bold glandular belts, 

 the representatives of tl.e scutes of other members of the 

 family. JJcsidi s, a great glandular semicircular lamella is 

 j)laccd immediately behind the spout-shaped fold of the 

 cephalic plate and separates the oral from the succeeding 

 region, and is evidently of great physiological importance. 

 A narrow glandular ring fuUows, tlie convex central region 

 being in some separated by furrows from the lateral regions, 



