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. The head and first two segments of the same seen from below, shewing the bucal 



aperture surrounded by thick lips. 

 2529. A gill of If 5'. h 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, b 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 s . 1 segment. 



PI. 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 

 Stroeraii (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 fig. 6. 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. 



