REPOKT ON THE DEEP-SEA MEDUSAE. 57 



four interradial pit-like depressions (figs. 6, 7, it) separated from one another by four 

 perradial vertical folds of the subumbrella (fig. 3, wr). These are Clark's " circumoral 

 buttresses;" they extend in the form of four free mesenteric lamella? from the four 

 perradial angles of the oesophagus to the middle of the subumbral wall of the radial 

 pouches, and are best described as reproductive folds or genital mesenteries (" mesogonics "). 

 The four depressions lined with the ectoderm of the subumbrella are the funnel cavities 

 (" infundibula," figs. 2, 6, it). The ctecal ends of these conical or trigonal pyramidal 

 hollow spaces penetrate from the coronal cavity of the umbrella deep into the central 

 gastral cavity, and have occasioned many misapprehensions. Clark calls them "circumoral 

 pouches," Taschenberg " genital pouches," Kling " pyramidal spaces," and Hertwig 

 " intergenital pouches." As these funnel cavities are only lined by the ectoderm and 

 have no connection with the gastrovascular system, but belong much more to the 

 system of the subumbral umbrella cavity, they cannot be termed " pouches " but merely 

 " cavities." They recur in the same way in many other Acraspedse as " subgenital 

 cavities." In our Lucernaria they penetrate so deep into the central gastral cavity as 

 to divide its oral half into four perradial peripheric niches, or " central chambers." 

 The conical funnel cavities between the latter are separated from them by the gastral 

 filaments, and pass directly above into the solid tseniola (fig. 21, ft). 



Tbe muscular plate of the subumbrella lies immediately under the ectodermal epithe- 

 lium, from which it is secreted, and consists of a marginal octomeral coronal muscle and 

 of eight separate radial muscles. The coronal muscle ("musculus coronarius"), or circular 

 muscle of the umbrella margin, is homologous with the simple marginal circular muscle of 

 the Tesseridse and with the large octomeral coronal muscle of the Pericolpidse, which in 

 the Periphyllidas is divided into sixteen muscular area?. The coronal muscle in the eight- 

 armed Lucernaridae, as in the closely-allied eight-lobed Pericolpicke, consists of eight 

 separate arese, the eight "marginal muscles," of which four longer (figs. 2, 3, 12, mm) 

 lie in perradial octants, four shorter (mm" ) in four interradial octants ; as, however, the 

 eight arms (or marginal lobes) are adradrial, each coronal muscular area (or each 

 marginal muscle) applies to the two halves of each two adjacent arms turned to 

 each other. It extends on their external or abaxial side, and that of the tentacles 

 running out from them. The separate bundle of muscles, which here pass into the 

 tentacles, therefore extend them and make them arch outwards (" extensores"). If, on 

 the other hand, all the eight marginal muscles contract simultaneously, they narrow 

 the umbrella opening like the simple circular muscle of the Tesseridae. The coronal 

 muscle is, moreover, in all Lucernaridae much narrower than in the Pericolpidae, and 

 has the form not of a broad band, but of a thick cord. In our species this cord 

 shows six to eight deep parallel furrows, divided from each other by the same number of 

 circular folds (fig 20 in radial transverse section). The height of these folds increases 

 from above downwards (from the proximal to the distal margin of the marginal muscle). 



(ZOOL. CHALL. EXF.— PART XII. — 1881.) M 8 



