Gattij Marine Lahora/on/j St. Andrews. 81 



in connection with the jirohoscis, which forms a compara- 

 tively hirge and thiciv-walled organ Mit'i a foliate arrange- 

 ment of its mucous lining ; an external coat of longitudinal 

 and an internal layer of circular muscular fibres, besides the 

 external sheath, are present. The mid-dorsal and mid-ventral 

 vascular trunks are large, the latter lying between the ventral 

 ends of the strong oblique muscles, which are inserted over 

 the neural canals, which are large and situated at the upper 

 border of the nerve-area, the rest of the area being hypo- 

 dermic. 



The first foot in a Canadian example (PI. VI, fig, 2) is 

 minute and consists of a fan-shaped dorsal lamella and a 

 smaller ventral one of ovoid outline, one side forming the 

 adherent base. In front of the dorsal lamella is a group of 

 strong tapering bristles, with a basal curvature and a very 

 fiuely tapered tip, the centre of each being minutely granular, 

 whilst the slender tip is homogeneous. The ventral tuft is 

 composed of bristles almost straight, but having as finely 

 tapered tips. No wings could be defined in the bristles of 

 this foot, and the tufts were nearly equal in size. 



In the second foot of the ('anadian form (PI. VI. fig. 3) 

 the dorsal lamella has become broadly lanceolate, its lower 

 border being bluntly round, the upper somewhat pointed. 

 The ventral lobe is elongate-ovoid, with the iree end pointing 

 downward. The curvature of the dorsal bristles is less 

 marked, the centre of the shaft is less distinctly granular, and 

 there is a barely visible trace of a wing. The ventral bristles, 

 on the other hand, aie more evidently curved, are larger, and 

 of two kinds — longer, curved, finely tapered forms, with 

 minute granules in the shaft, and a finely tapered tip, 

 without wings ; and shorter bristles, with translucent shafts, 

 narrow wings, and finely tapered tips. 



The third foot of the Canadian form has a considerably 

 larger dorsal lamella, and has the pinnate process in front, 

 but it carries no branchia. The next two feet (fourth and 

 fifth), however, bear well-developed branehite (PI. VI. tig. 4), 

 that following (sixth) having a conspicuous dorsal lamella 

 and a pinnate process on each side. In the succeeding feet 

 tiie dorsal lamella gradually diminishes, so that at the fourth 

 from the posterior pinnate process both lamellte are much 

 reduced, and the capillary bristles thus rendered conspicuous. 

 Posteriorly the lobes of the feet diminish greatly, whilst the 

 dorsal bristles become longer and so slender as to be hair- 

 like. Ventrally hooks take the place of the inferior bristles 

 from the fifteenth foot backward. In this form the pinnate 

 or papillose cirri (PI. VI. fig. 1, t.) were sparsely covered 



Ann. (fc Mnq. N, Hist. ISer. S, Vol. xiij. 



