voL.xvi.j PROCEEDINGS OF THE NATIONAL MUSEUM. 157 



1893. 



(lio'j beiii.i; (•(Histricted just at their insertion into the disc, being \Yidest 

 just distal to the constriction ; consequently they readily fall oft", leaving- 

 a round opening in the disc. These openings are, ho^yever, ])artially 

 closed ]»y a muscular fold of mesogkea arising from their margins, and 

 similar to what has been already described for B. oecidud* Notwith- 

 standing their close similarity in the structure, the tentacles have a 

 very different appearance from those of the species Just mentioned. In- 

 stead of being i)lump, turgi<l, and robust, they are flaccid, flattened, 

 and rather slender, and give to the preserved specimen a very ragged 

 and torn appearance. It is on this account that I haAC bestowed upon 

 the species the name pannosa. 



The musculature of the tentacles is weak, the ectodermal muscles 

 not being imbedded in the mesogkea (PI. xxii. Fig. 28), but supported 

 by hardly noticeable mesogheal elevations. The longitudinal ridges of 

 mesoghea wlii<;^i give to the tentacles of the Bolocerid;c their fluted 

 appearance are readily to be seen in the tentacles of the inner cycles, 

 but they are not so well developed as in other species of Bolocera. 



The disc is almost entirely covered by the tentacles, only a relatively 

 small area around the mouth being naked. Its ectodermal nniscles 

 are weak, though the endodermal circular system is fairly well devel- 

 oped; less so, however, toward the margin. 



The stomatoda^um is prominent and ]»ossesses two siphonoglyphes. 

 The mesenteries are numerons, there being probably about ninety-six 

 pairs, of which twenty-four are perfect and non gonophoric (two of them 

 being directives), twenty-four well developed, though not perfect, and 

 forty-eight relatively small. All the imperfect mesentenes are gono- 

 phoric. The muscnlature of the mesenteries is not particularly strong, 

 but i)resents a very peculiar arrangement. If a transverse section of 

 a mesentery of the first cycle be examined (PI. xxi, fig. 20) it will be 

 seen that at its attachment to the column wall it is comparatively thin; 

 it soon, however, becomes thicker, and numerous cavities, containing 

 apparently the degenerated remains of cells, are seen in the mesogkea. 

 The exocrelic face of this portion of the mesentery bears muscle proc- 

 esses which are cut transversely {pbm), and therefore give support 

 to longitudinal muscles, or rather to the obli(jue muscles forming the 

 parieto-basilar muscle. The inner edge of this muscle is to a slight 

 extent frex^ from the mesentery, and it seems as if the cavities had been 

 produced by the fusion at intervals of the mesogloea of this free v(}ge 

 with that of the mesentery during the growth of the animal. P>eyond 

 the region of the parieto-basilar nniscle the mesogkea becomes thinner, 

 and its exocrclic surface is covered by a simple layer of muscle cells 

 whose fibres intermd to the i)arieto-basilar region run longitudinally, 

 then becanu' transverse, and finally near the insertion of the nu'sentery 

 into the stomatodaMim become again longitudinal, being now supjiorted 



"See note ]}. 151. 



