79 



Fig. 21. The posterior part of the body seen from below. 



— 22. The anterior part of the body of a living specimen with only 4 pairs of gills, seen 



from above. 



— 23. The same seen from the right side, shewing the main blood-vessels. 



— 24. Tlie head and first two segments of the same seen from below, shewing the bucal 



aperture surrounded by thick lips. 



— 25—29. A gill of 15'— ,5'!' pair, shewing the progressive dichotomic division. 



— 30. Section of one of the gill-bearing segments. 



— 31. Section of one of the middle segments of the body. 



— 32. The dorsal pedal tubercle, with the rudimentary dorsal cirrus, more strongly magnified. 



— 33. The ventral pedal tubercle, with the ventral cirrus. 



— 34. Pedal bristles, a, h of the dorsal; c, d, e, of the ventral pedal tubercle. 



— 35. The double chitine hooks which are attached to the dorsal pedal tubercle of the 



1'.' segment. 



^]. V. 



Fig. 1—23. Mopsea borealis. 



(All the figures excepting 7', 8, 9 and 10 of natural size.) 

 Fig. 1. The largest colony found, of which however the root is wanting. 



— 2. Another specimen, on the top of which are attached 2 specimens of Scalpellum 



Stroemii (a. a). ^ 



— 3. A complete undivided colony, with root. 



— 4. An other colony, somewhat branched. 



— 5. The upper part of a colony, branched in an unusual degree. 



— 6. An undivided living colony, with extended polyps. 



— 7. A quite young specimen, with only a single terminal polyp. 



— 7'. A piece of the stem of the same specimen, shewing the exterior skin and a horny 



joint, strongly magnified. 



— 8. The upper part of the specimen delineated rig. 0. with partially extended polyps. 



— 9. Calcareous spicula from the skin of the polyps. 



— 10. Extremity of such a spiculum, strongly magnified. 



— 11. (Above fig. 1). A piece of the axis consisting of 3 joints, of which 2 belong to 



the main axis; the third, springing out from the knee, forms the beginning of a 

 lateral branch. 



— 12. A piece of the axis, consisting of 3 elongated calcareous joints. 



— 13. An other piece of the axis of a larger colony, likewise consisting of 3 calcareous 



joints connected by knees. 



— 14. A third piece of axis, consisting of 6 calcareous joints. 



