ventrale Flade forsynet med næsten ægformige Kalkplader, 

 der sidde paa hver Side af Midtfuren og tjene for en Del 

 til at dække denne. De sidde afvexlende og ere befæstede 

 med den smalere Ende til Randene af den ventrale Flade, 

 nærmest Midtfuren. 



Det ellevte Brachiale danner et Syzygialled, og her 

 tager den første Pinnula sit Udspring fra Leddets epizy- 

 giale Del, Tal). II, Fig. 3 c. Denne afviger noget i Form 

 fra de foregaaende Led derved, at der paa den distale 

 Ende er et buet Indsnit, som optager omtrent Halvdelen 

 af Sideranden. og som udgjor Leddefladen for Pinnulens 

 første Led, Tab. II, Fig. 3 d. De epizygiale Led ere der- 

 for temmelig usymmetriske, idet den Rand, hvor Indsnittet 

 findes og Pinnulaen insererer sig, er meget kortere end den 

 modsatte, hvor ingen Pinnula findes. Som ovenfor nævnt 

 sidde Pinnulerne i to hinanden modsatte, afvexlende Rækker, 

 og dette i Forening med det Usymmetriske i Leddenes 

 Siderande giver Armen tildels et noget vredent Udseende. 

 Som jeg ovenfor har nævnt, tog Pinnulerne, der vare 22 i 

 Antal paa en Arm af 26"""'s Længde, deres Begyndelse 

 fra det Ilte Leds epizygiale Ende. 



Pinnulerne have en Retning opad og lidt udåd, noget 

 hoiede efter Længden, ere lancetformede, sta^rkt hvælvede 

 til Siderne og meget hule paa Ventralfladen, Tab. II, Fig. 

 3 c, e. De første Pinnuler have en Længde fra 2 — 3""", 

 ere omtrent 1'"'" brede; de derpaa følgende 4 ere de længste, 

 4""" lange. I"'"" brede paa Midten og 0.5""" ved Basis; efter- 

 haanden aftage de nu saavel i Længde som i Bredde, saa 

 at den øverste er 1.2""" lang. De 3 nederste beståa af 

 7 lange, smale Led, de 4 længste af 9 Led, og de øverste 

 kun af 4 og 3. Mellem første og andet Led er et Syzy- 

 gium. Endeleddet er temmeligt afstumpet. 



Det første Leds proximale Ende har en Leddeflade, 

 der mod Dorsalfladen har et halvrundt Indsnit for Insertion 

 af elastiske Baand. og mod Ventralfladen to smaa Sidefor- 

 dybninger for Muskelinsertioner; imellem disse en liden, 

 rund Aabning til Gjennemgang for en Gren af Central- 

 strængen. Leddenes dorsale Flade er meget konvex, den 

 ventrale meget konkav og Siderne konvexe, hvorved en dyb 

 Længdefure fremkommer, som er forsynet med to Rækker 

 temmelig lange, eylindriske Tentakler, der paa deres udven- 

 dige Flade ere besatte med smaa, koniske Papiller, Tab. I, 

 Fig. 12 t. Denne ventrale Fure kan for Størstedelen lukkes 

 af to Rækker Klapper, en paa hver Side. 



Disse Klapper ere i Antal forskjellige efter Pinnu- 

 laens Længde ; i Regelen er der to Klapper paa hvert Led, 

 men de midterste Led ere tildels forsynede med fire saa- 

 danne, to paa hver Side. De ere ovale, længere end Fu- 

 rens Bredde, og vende med den smalere Del mod dens 

 Insertionspunkt. medens den bredere, næsten runde Del 

 har sin fri Rand vendt indad mod Furen. De ere fæstede 



and are furnished on the ventral surface with almost ovi- 

 form calcareous plates, which are seated on each side of 

 the medial groove aud' partially serve to cover it. They 

 are seated alternatingly, and are attached with the narrower 

 extremity to the margins of the ventral surface, next to 

 the medial groove. 



The eleventh braehial forms a syzygial joint, and here 

 the first pinnule has its origin in the epizygial portion of 

 the joint (Pl. II, fig. 3 c). This (lifters somewhat in shape 

 from the preceding joint, from there being, on the distal 

 extremity. a curved incision which occupies nearly the half 

 of the lateral margin and forms the articular surface for 

 the first joint of the pinnule (Pl. II, fig. 3 d). The epi- 

 zygial joints are therefore pretty unsymmetrical, as the 

 margin where the incision is found and the pinnule inserts 

 itself, is much shorter than the opposite one, where no 

 pinnules are found. As stated above. the pinnules are 

 seated in two alternating series opposite to each other, 

 and that. in connection with the absence of symmetrv in 

 the lateral margins of the joints, imparts to the arm. partly. 

 a somewhat twisted appearance. As I have mentioned 

 above, the pinnules — which were 22 in number on an 

 arm 26""" long — commence on the epizygial extremity of 

 the eleventh joint. 



The pinnules are directed upwards and slightly out- 

 wards, are somewhat Longitudinally curved and lanceolate, 

 are strongly arcuated to the sides, and very hollow on the 

 ventral surface (Pl. II, fig. 3 c, c). The first pinnules are 

 2— 3" 1 "' in length, and about l'" m in breadth; the 4 follow- 

 ing thereafter are the longest, 4""" long, 1""" broad in the 

 middle and 0.:.'""' at the base, they then gradually diminish, 

 both in length and breadth, so that the length of the up- 

 penuost ones is 1.2""". The three lowest pinnules consist 

 of 7 long. narrow joints; the fonr longest ones of 9 joints, 

 and the uppermost ones of only 4 and 3 joints. Between 

 the first and second joint there is a syzygiuiu. The terminal 

 joint is pretty obtuse. 



The proximal extremity of the first joint has an ar- 

 ticular surface which, towards the dorsal surface. has a 

 semi-circular incision for the insertion of elastic bauds, and 

 towards the ventral surface has two small lateral cavities 

 for muscular insertions; between these there is a small 

 round aperture for the passage of a branch of the central 

 cord. The dorsal surface of the joints is very convex, the 

 ventral surface very concave and the sides convex, pro- 

 ducing, thus. a deep longitudinal groove which is furnished 

 with two series of pretty long. cylindriform tentacles that. 

 on the outer surface, are covered with small conical papillæ 

 (Pl. I, fig 12 t). This ventral groove may. for the greater 

 part, be closed by two series of valves. one on each side. 



These valves are variable in number according to the 

 length of the pinnules; as a rule there are two valves on 

 each joint, but the medial joint is partly furnished with 

 four such valves. two on each side. They are oval. longer 

 than the breadth oi the groove, and face with the nar- 

 rowest extremity towards their point of insertion, whilst the 

 broadest, almost round portion, has its free margin turned 



