51 



broken at the end; and at the distance of about 60 Mm. from the root, an other branch 25 

 Mm. long, nearly at a right angle. Both branches are about of the same thickness as the 

 main stem. Another specimen of the same size, or even a little higher (fig. 3) was, like the 

 first observed, entirely undivided with a tolerably straight stem. A third specimen (fig. 1) 

 was considerably larger, namely 105 Mm. high, but yet incomplete; as the whole lower part 

 was wanting. It had at a distance of 45 Mm. from the point, one single branch 35 Mm. long 

 issuing nearly at a right angle. A fourth imperfect specimen (fig. 5) probably the exterior 

 part of an equally large exemplar, had 2 nearly equally large branches issuing close together 

 from the stem, but in dift'erent directions, one at a right angle, and the other at an acute 

 angle, and besides these one very small branch near the end. This is the most extensive 

 branching which I have observed. 



As will be seen from the above, the coral under consideration seems to be very, 

 slightly branched; the stem being -either completely undivided, or only here and there exten- 

 ding a short lateral branch, which appears never to divide itself again. Hereby the form is 

 very decidedly distinguished from the other Isidse, which are always extensively, most fre- 

 quently dichotomically, branched. 



As in the other forms belonging to- this sub-family, the stem, as well as the branches, 

 consists of a solid axis formed of alternate calcareous and horn-joints, and a soft and fleshy 

 envelope (cnenenchym), covering this axis, wherein the polyps reside. The lower half or third 

 part of the stem seems however always to be sterile (see fig. 2. 3. 4. 6); and it is very diffi- 

 cult to distinguish on this ])art any sort of envelope, which yet must certainly exist originally 

 also here in the form of a thin membi-ane. The whole axis is very slender, cylindrical and 

 everywhere (excepting at the root, and at the extremity which terminates in a narrow point) 

 of nearly uniform thickness. In the above mentioned exemplar (85 Mm. high) the axis was at 

 the basis scarcely 1 Mm. thick. In the upper part, the coral seemed certainly to be some- 

 what thicker; but this is attributable solely to the exterior polyp-bearing evelope (csenenchym) 

 which is here rather strongly developed, and in fresh exemplars is often double as thick as 

 the axis. The joints of the axis are generally extremely elongated, but of somewhat unequal 

 length, often strongly curved (see tig. (i. 12. 22 i*tc.) completely calcareous and connected with 

 each other by very short horny articulations or knees. By means of these latter, the sub- 

 stance of which is somewhat elastic, the stem becomes flexible: for the calcareous joints are 

 completely stiff and inflexible. The lower part of the stem resolves itself into several (3 — 5) 

 irregularly curved and folded completely calcareous blades, which fasten themselves do.wn be- 

 tween, and partly grasp, the harder particles of clay or grains of sand which lie above the 

 mud that covers the bottom of the sea, and thus, as it were like root-leaves, serve to attach 

 the colony. The latter seems therefore, unlike most of the other corals, to be only slightly 

 attached. 



Most frequently these root-leaves are so arranged (see fig. 3. 4. 6. 18) as to form 



together an inverted very short and wide funnel; the stem immediately below the first knee 



7* 



