80 ARENICOLA BRANCHIALIS. 



Elsewhere it occurs on the shores of the Mediterranean, French coast, the Atlantic, 

 and the Black Sea, 



The Snout forms a blunt cone, the tip of which is rugose, the furrows being longi- 

 tudinal, and a bifid process occurs beneath in the middle line in front. Posteriorly it ends 

 in the median bite which has a border behind, and the sides of which in front project 

 inward, the nuchal groove then turning slightly backward and downward to the ventral 

 surface. In softened specimens the aspect differs, the head having a median peak pos- 

 teriorly from each side of which a band passes obliquely outward and backward, though 

 they are often covered by the deep fold behind. In extrusion of the proboscis, the 

 median neck or band is conspicuous when the posterior fold is drawn back, and the lateral 

 bands are nearly transverse. In some the median process of the head fits into the notch 

 in the ring behind, the edges of the notch being fixed to the sides of the median process, 

 and it is probably these which in softened specimens have the aspect of bands. In others 

 no notch exists in the ring behind the head, the edge of the segment passing evenly round 

 to the ventral surface, and the lateral fold on each side of the median process is less 



KGa__ 



Pk. 



Fig. 109. — Snout of Arenicola branchialis from the dorsum. N. Gr. Nuchal groove. Pr. Prostomium. 



After Dr. Ashworth. 



distinct. Considerable variation thus exists both in regard to states of contraction of the 

 lateral folds and the edge of the ring behind the head. 



The arms of the nuchal groove follow the same direction as those of A. ecaudata 

 (p. 74), but the lips are more closely apposed. The organ has the same innervation. 

 The position of the statocyst in the peristonium is indicated by a slight depression a little 

 dorsal to the point of intersection of the second of the circular grooves with the meta- 

 stomial grooves (Gamble and Ashworth). 



The ventral nerve-cord has a single neural canal in front. In segments five to ten, 

 two, in the central region of body three, and posteriorly only one. They arise from the 

 giant-cells of the cord (Gamble and Ashworth). Byes present in post-larval forms as in 

 A. ecaudata. 



Length 8 or 9 in. or perhaps more. Of a uniform blackish-green colour with bluish 

 iridescence ; branchiae dull red. A small tail exists in some behind the last bristles, two 

 of which occasionally exceed the line of the branchiae. The green tint emitted on immer- 

 sion in spirit is strikingly beautiful. There are eleven anterior abranchiate segments. 



Small forms from low- water mark, Lochmaddy, about 2 in. long, are of a uniform 

 straw-yellow colour, with finely branched branchiae, and the extruded proboscis is also 

 yellow. Ashworth again records adults as generally very dark— from bluish-black to 

 dark green. 



The proboscis corresponds generally with that of the other British forms, the large 

 basal papilla? also often being dark. In small examples from Naples the proportion 



