Gutty Marine Lahoratory^ St. Andrews. 163 



sharp main fang comes off nearly at a right angle and the 

 rrown has a single sharp spike. This form was dredged iu 

 8 fathoms in Bressay Sound. MesniPs Spio martinensis *, 

 which he hints may yet be linked on to Spio Jilicornis, 

 O. Fabr., ditiers in the form of the head, since it has no 

 fissure in front, bnt the author's drawings perhaps need more 

 definition. Moreover, he mentions no occipital tentacle. 

 The number of segments, the size, and the general structure 

 of the tail, feet (from the 1st backward), and bristles agree, 

 yet in the British form the latter are not punctated, a 

 feature of moment, for only longitudinal striae are visible 

 even in the inferior ventral. 



Spio seticornis, Fabr., has a head produced anteriorly into 

 a rostrum, with two small frontal tentacles, the central region 

 supported by the buccal segment on each side. It is about 

 an inch in length, little tapered anteriorly, and gradually 

 diminished posteriorly. The branchiae commence on the 

 first segment and apparently continue to the posterior end. 

 They seem to be conspicuous about the middle of the body. 

 The foot has a narrow and prominent superior lamella in 

 front and a small conical lower lamella. The former 

 diminishes posteriorly and the latter becomes flattened out 

 as a narrow rim. The bristles present a long dorsal group 

 and a shorter lower group in the superior division, and a 

 similar short group in the ventral division anteriorly ; but at 

 the 8th bristled segment the place of the latter is taken by 

 winged hooks, the main fang of which comes off at a large 

 angle from the neck and is not very acutely pointed, the 

 rounded crown bearing a single spike. 



This diflers from the previous form in so far as the hooks 

 appear before the 10th bristled segment, probably at the 

 8th. Thus at the 5th foot the branchia is well developed, 

 whilst the upper lamella passes outward and upward as a 

 broad conical flap, and the bristles form a diminishing series 

 from above downward. The inferior lamella is small, 

 torming a short blunt cone pointing below the setigerous 

 process. At the 10th foot the branchia is larger and appa- 

 rently flattened, the upper free edge above the superior 

 lamella is shorter. The superior lamella is small at the 25th 

 foot, but the branchia remains large ; it becomes less at the 

 50Lh foot, it is difficult to say what the Spio seticornis, 

 Fabr., ot Cunningham and Ramage f is. Mesnil tiiinks it has 



* Bullet. Sc. Fr. Belg. xxix. p. 122, pi. vii. figs. 1-20 (ISQH)- 

 t Trans. Rov. Sue. Ediu. vol. xxxiii. p. 64U, pi. xxxvii. figs. 4, 4 a, 

 & 4 b. 



