464 G. M. R. Levinsen. 



Porella concinna, granular var., Hincks, Ann. Nat. Hist. ser. 6. Vol. 



IX, p. 156, pi. VIII, fig. 6. 

 Porella plana Waters, op. cit. p. 79, PI. XI, figs. 11—13. 



I have seen a small fragment of an old two-layered colony. 

 St. 95 a. The Sound between Renskæret and Maatten, 50 — 100 m. 



Porella fragilis n. sp. 



Porella eleganhila, var. rostrata Hincks, Annals Nat. Hist. ser. 6, Vol. 

 I, 1888, p. 223, PI. XV, figs. 5, 5 a, 5 b. 

 (PI. XXII, figs. 4, 5, 6, 7, 8, 9). 



The zooecia have no pores and no spines, and the calcareous 

 substance is very thin, brittle, and hyaline; they are very long (about 

 thrice as long as broad) rhombical, somewhat compressed and pro- 

 vided with a very convex frontal surface, the two lateral halves of 

 which form an obtuse angle with each other. The aperture, which 

 is perfectly concealed by the distal end of the avicularium, when 

 the colony is regarded from the frontal surface, is placed in the 

 very distal end of the zooecium, and forms an angle with the longi- 

 tudinal axis of the zooecium, not much larger than a right angle. 

 It is about half-elleptical, provided with a rather short, faintly pro- 

 jecting margin and with an oral keel, the proximal end of which 

 is developed as a small hinge-tooth. The operculum is membranous 

 or very faintly chitinized and provided on each side with a fairly 

 long and very muscular ridge obliquely distally directed. The 

 vestibulum is fixed to the very margin of the operculum. Each of 

 the lateral walls is provided with an ovate rosette-plate with 3 — 5 

 pores placed in the angle between its distal and proximal portion, 

 and corresponding to a hole placed in the proximal end of a neigh- 

 bouring zooecium. In most cases a larger or smaller portion of this 

 rosette-plate reaches the basal wall, and in that case it may also be 

 regarded as a pore-chamber. The obliquely ascending distal Avail, the 

 proximal margin of which is not rarely angularly bent, is provided 

 near to the latter with с 6 — 8 pores, divided into various numbers 

 of uniporous or polyporous rosette-plates. In a number of zooecia 

 the basal wall is also provided with 1—3 rosette-plates with 1 — 4 

 pores or with as many holes. The ooecia which are provided with 

 a flat shaft-like proximal portion of somewhat different length 

 speedily increasing in breadth, are very convex, longer than broad 

 (when the shaft-like portion is included about half as long again 

 as broad); the distal half of their basal wall may easily be separated 

 from the adjoining frontal wall of the distal zooecium. The ecto- 

 ooecium is calcified in its whole extent. 



