530 



THE FUR SEALS OF THE PRIBILOF ISLANDS. 



Zi. 



Synoicum irregulare, new species. 



General character of the colony. — In. all cases distinctly lobed, but the lobes very 

 variable in size and shape. In some instances they are separate almost to the base 

 of the colony, while in others the upper half or even lei^s of the entire length of the 

 lobe is free from the common basal mass. Some of the lobes decidedly enlarged at 

 the summit, others not so. An occasional lobe stands out at 

 nearly a right angle to those with which it is in closest relation. 

 Earely any free spaces between the free portions of the lobes. 

 No longitudinal furrows on the lobes marking the intervals be- 

 tween the zooids, though the zooids quite clearly visible through 

 the test on the sides of the lobes. Surface of the test at the 

 bases of the lobes and of the basal undivided mass often shows 

 well-marked transverse corrugations (lig. 2G). Color of the lobes 

 milk wliite; of the basal portions grayish. This appears to be 

 the predominating color characterization, but some colonies gray 

 throughout. Very little sand or other foreign substance on the 

 surface. Test relatively large in quantity, semicartilagenous, no distinct surface layer. 

 Cells very numerous. Basal portions traversed by a few vessels. Height of largest 

 colony, .'5 cm.; length of longest lobe in this colony, 17 mm.; 

 thickness of base of this lobe, 8 mm.; thickness of summit ^ 



of same lobe, 1.'} mm. These values would not appear to be 

 greatly above the a\ erage. 



Zooids. — From two or three to eight or ten in each lobe. 

 Not visible on the summit of the lobes in any of the specii- 

 meus at hand, but quite distinctly so on the sides of the lobes 

 in some (colonies. Of large size, always at least as long as 

 the lobes of the colony, usually extending to very near the 

 base of the colony. Average length about 17 mm. Of this, 

 considerably more than half is post-abdomen. Thorax rela- 

 tively very short in all specimens at hand, but this largely 

 due to great contraction. Post-abdomen not pedunculated 

 (fig. 28). Condition as to systems in doubt. Api)arently a 

 common cloac^a not usually present, but material at hand 

 does not permit final determination of the point. 



In some colonies zooids in a peculiar state of disorganiza- 

 tion. (This subject moie fully treated in another connection.) 

 Musculature consisting almost exclusively of longitudi- 

 nal fibers; these not disposed in bundles to the usual extent 

 in compound ascidians. 



Branchial apparatus. — Neither of the orifices found with 

 certainty on the surface of the colony in any of the speci- 

 mens at hand. In the few colonies in which the thorax is 

 present at all, so much contracted and so thick walled that 



its structure could be but imperfectly determined, liranchial siphon six-lobed; these 

 thick and rather obscure. Atrial orifice obscmrely unequally lobed. A short and 

 thick atrial languet present; its lobulation not determined. Tentacles not large or 

 numerous, of unequal sizes. 



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