Gatty Marine Lahoraiory^ St. Andrews. 41 



a bird's head. Above the main fang tlie rounded crown lias a 

 series of lour sraaller teetii. This kind of book is cbarac- 

 tei'istic of the biistle-bearing segments. 



A series of vertically flattened nncinigerous lamellfB occur 

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

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

 avicular books, having short, broad, basal ])rocesses with a 

 convex inferior outline, a posterior outline in which a deep 

 sinus occurs above the basal process, and an anterior outline 

 which in some has a trace of a process beneath the main 

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

 it are proportionally large, so that this hook does not 

 present the disproportion between the Hrst and succeeding 

 teeth present in the long anterior liooks. In lateral view 

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

 they form a rounded crown with their ])oints curved obliquely 

 downward. Malingren, while noting the distribution of the 

 hooks from front to rear, does not sufficiently define the 

 structure of the posterior hooks. 



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

 bellides stroemi, Sars, in wliich the cephalic region is almost 

 as blunt as in TrichobrancliKS, though the great elevation of 

 the frilled cephalic plate is characteristic, since it rises from 

 a slight collar high above the dorsal outline and has a boldly 

 folded inaigin, the two sides meeting in the middle line 

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

 wliich behind the mouth in some are thickened. The cephalic 

 plate thus has the surfaces directed anteriorly and posteriorly, 

 instead of dorsally and ventral ly as in Foly cirrus 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 the scutes of other members of the 

 family. J3esid( s, a great glandular semicircular lamella is 

 placed 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 follows, tlie convex central region 

 being in some separated by furrows from the lateral regions, 



