PLATE XVIL 



Archangelopsis typica no v. gen. no v. spec. 



Abbreviations. 



po = pneumatocodon (Luftschirm). 



exo = ectodermlayer of the pneumatocodon. 



fo = chitinouslayer of the pneumatocodon. 



eno = entodermlayer of the pneumatocodon. 



p.sacc = pneumatosaccus (Luftsack). 



^xac = ectodermlayer of the pneumatosaccus. 



fac = chitinouslayer of the pneumatosaccus. 



enac = entodermlayer of the pneumatosaccus. 



p. cav = pericystic cavity. 



py = pneumatocyst (Luftflache). 



c. py = club-shaped enlargement of the pneuma- 

 tocyst. 



y.py = folds of the same in the secondary ectoderm, 

 situated in the pneumatosaccus. 



p. oy = pneumatopyle (Trichterpforte). 



pe = pneumatochone (air-funnel, infundibulum, Luft- 

 trichter). 



sec. exy = secondary ectoderm in the pneumatochone 

 (pneumadenia) and in the cavity of the pneuma- 

 tosaccus. 



r. s = gigantic cells in the secondary ectoderm. 



cav. sec = cavities which are formed by the gas- 

 secreting secondary ectoderm. 



b. a ^ buds of youngest appendages. 



s.a. cc = transverse entodermal septa, connecting the 

 pneumatochone and the pneumatocodon. 



s. s. (S = transverse entodermal septa connecting the 

 pneumatosaccus and the pneumatocodon. 



a. s = appendages of the siphosome. 



a. s. a = buds of nectophores (?). 



Fig 

 Fig 

 Fig 



Fig. 124. A reconstruction of a median longitudinal section through a typical Angelid (after sections 

 through three specimens of Arcliangelopsis typica nov. gen. nov. spec, enlarged about 25 X. 

 (Ectoderm = yellow, chitinous layer = black, entoderm = grey, secondary ectoderm = green) 

 Semi-diagrammatical. 



125 I. A longitudinal section of the same showing part of the pneumatosaccus; first appearance of 

 the air-funnel after section through the youngest appendages (glass i — 10 III 7). Abbreviations 

 as indicated above (Cat 10 K. ix. glass 10 III 8). ± 25 x. 



126 II. The same, the buds of appendages on this figure and the next (126 — 133) are left out. (Cat. 

 10 A. (X, glass II II 4) ± 25 X. First appearance of the club-shaped enlargements of the pneu- 

 matocyst as an odd spherical body of chitinous substance in the air-funnel. 



127 III. The same (Cat 10 A. x glass 11 III 3). The air-funnel approaching the pneumatosaccus, both 

 their chitinous layers uniting, paired club-shaped enlargements increasing in size. ± 25 X. 



128 IV. The same (Cat. 10 A. x glass 11 III 7). The chitinous layer of the pneumatosaccus shows an 

 interruption, the club-shaped enlargements are connected by a thread, which faces the pneu- 

 matocyst. ± 25 X. 



129 V. The same (Cat. 10 A. x glass 12 I 4). The thread of the club-shaped enlargements unites on 

 both sides with the chitin of the pneumatocyst. The pneumatocyst with its chitinous ring is 

 now clearly recognizable. This time we may speak of pneumatopyle (Trichterpforte). ±: 25 X- 



130 VI. The same (Cat. 10 A. x glass 12 II 5). Formation of cavities in the secondary ectoderm, 

 both in pneumatochone and near pneumatosaccus. -\\ 25 /. 



131 VII. The same (Cat. 10 A. x. glass 13 I 4) ± 25 X. The same cavities increase in size. Compare 

 this sketch with Fig. 136 of PI. XVIII. 



132 VIII. The same (Cat. 10 A. « glass 13 I 7). The cavities become spherical again and are separated 



one from the other by secondary ectoderm. ± 25 . 

 Fig. 133 IX. The same (Cat. 10 A. x glass 13 III 5). The same cavities close again. ± 25 X- (N.B. By 



mistake IX has been omitted on the plate). 

 One of the youngest buds of appendages, greatly magnified (Cat. 10 A. x glass 12 II 7). 220 X. 

 Secondary ectoderm cells with part of a branched liiant-cell (black granulation). (Cat. 10 A. x 



glass 13 II 6). 220 V. J 



Fig. 



Fig. 

 Fig. 



Fig 



Fig 

 Fi? 



134- 

 135- 



