REPORT ON THE DEEP-SEA MEDUSAE. 81 



at the umbrella margin (as in the Lucemaridse and Chary bdeidas). The correctness of this 

 morphological view is also justified by comparison with the important common parent 

 group of the Tesseridse (System, p. 369, taf. xxi.). 



The large coronal sinus is divided by the upper or proximal margin of the coronal 

 muscle from the marginal pouch corona, which forms the principal section of the 

 peripheric coronal intestine ("corona bursarum," PL XXI. figs. 12, 13, 19, 20 ; PL XXII. 

 fig. 22 ; PL XXIII. figs. 29-32 ; PL XXIV. fig. 1). This corona is composed of the sixteen 

 coronal pouches and the canals which run from them into the four sense clubs, the twelve 

 tentacles, and the sixteen marginal lobes. The sixteen coronal pouches ("bursas coronares," 

 be) into which the lower or distal margin of the circular sinus opens (at the proximal 

 margin of the large coronal muscle), correspond in number, shape, and size to the sixteen 

 coronal plates or the separate trapezoid muscular areas of the large coronal muscle (me). 

 They are shallow quadrangular pouches, whose inner or axial wall is formed by the 

 folded muscular area itself, its outer or abaxial wall by the smooth internal surface of the 

 gelatinous umbrella on whose external surface there is a pedalium corresponding to each 

 coronal pouch. The upper or proximal margin is formed by the horizontal narrow 

 cleft, by which it communicates with the coronal sinus ; it corresponds to the subumbral 

 boundary line between the coronal muscle and deltoid muscle. The two lateral (or 

 radial) margins are formed by the lobe clasps (M), by which each coronal pouch is divided 

 all its length from the two neighbouring pouches. As each lobe clasp cuts a marginal 

 lobe all its length into two halves, each coronal pouch belongs to the adjacent halves of 

 two lobes and sends out an evagination, the lobe pouch (" bursa lobaris," or lobe canal, 

 " canalis lobaris," fig. 22, bl ; fig. 29, bl) into each of these halves. As the lobe clasp 

 (M) only halves the upper or proximal part of the lobe and leaves the lower or distal 

 part free, both pouches of each lobe are in open communication below the clasp. They 

 consequently form a horseshoe-shaped canal, whose two parallel limbs are directed 

 centripetally and only separated by the septum of the lobe clasp (horseshoe canal, "bursse 

 hipposideri," fig. 22, bw ; fig. 29, bu). its proximal openings are in two adjacent 

 coronal pouches. If we fill one of the two lobe pouches of a coronal pouch with air, the 

 air passes through the U-shaped canal into the adjacent coronal pouch (fig. 22, bu). In 

 this way there actually arises in all Peromedusae a connective circular canal at the 

 umbrella margin, which in some measure resembles the festoon canal of the Narco- 

 medusse, runs along the margin of all the lobes, and puts all the coronal pouches into 

 peripheric communication. In the Pericolpidse, this wide festoon canal or marginal 

 canal (" canalis marginalia," cm) is composed of eight coronal pouches and sixteen lobe 

 pouches, whilst in the Periphyllidse it is composed of sixteen coronal pouches and thirty- 

 two lobe pouches (comp. my System cler Medusen, taf. xxiii. xxiv.). 



As the four interradial areas of the coronal muscle corresponding to the sense clubs are 

 considerably narrower than the twelve remaining areas corresponding to the tentacles, the 



(ZOOL. CHALL. EXP. — PART XII. — 1881.) M 11 



