318 
Fig. 11. Odontotheca  trispinosa Cought. A pair of hydrothecae, seen 
from the frontal surface of the branch. The stalk-mark shows 
a translucent inner cavity. X 47. 
— 12—13. The same species. The distal end of a hydrotheca, seen in 
two slightly different positions, but mainly from the adcauline 
surtace and partly from above. In fig. 18 is seen the translucent 
abcauline. sinus. "The line springing from the adcauline tooth 
indicates the ridge of the angularly bent adcauline membrane. X 66. 
— 14. An optical longitudinal section of a hydrotheca showing the 
inner cavity of the stalk-mark. X 75 
— 15, The same species. AÅ hydrotheca seen from the åbcauline sur- 
face. Distally is seen the abcauline opercular membrane. For 
the rest compare with Pl. IV, fig. 24. X 47. 
— 16. A gonotheca of Hebella contorta Markt. X 34. 
— 17. The same gonotheca seen from the distal end. X 34. 
— 18. Idia pristis Lmx. A portion of a branch seen from the frontal 
surface. Near to the distal end of each hydrotheca is seen the 
fold "of tlie adcauline opereular membrane (also seen in the 
othér figures). X 34. 
— 19. The same species. Dorsal view. Distinct stalk-marks. X 34. 
— 20. The same species. A somewhat oblique longitudinal section, 
which has cut away the distal ends of the one series of hy 
thecae. Distinct stalk-marks. x 34. 
— 21. Theé såme species. The distal end of a hydrotheca, seen from 
the adcauline surface. X 66. 
— 22. The såme, seen from the abcauline surface. The presence of a 
special abcauline opereular membråne is only faintly indicated. 
The ådcauline sinus with its median prøjection is seen through 
the thin wall. Xx 66. 
Literature. 
Allman, G. J: - Report on the Hydroida eolleeted during the expedi- 
tions of H. M. S. "Porcupine” (Transaetions of the Zo- 
ological "Society of London, vol. VII, part. VIIE, 1874, 
pag. 469—481, pils. 65—68). 
vre A monograph of the Gymnoblastic or AeDclarisn Hy- 
droids (Ray Society, London, 1871). 
— Diagnoses of new genera and species of Hydioide 
(Journal Linnean Society, Zoology, vol. X1I, 1876, 
p. 251—284, pls. IX-—XXIII). 
ne Report on the Hydroida -colleeted during the explo- 
ration of the Gulf-stream by L.F . de ler (Memoirs 
of Harvard 
at 
College, V, No. 2, Cambridge 1877, pag. 1—66, pls. 
XXXIV) 
