HYDROIDA. BALE. 275 



Sertularia brevicella, Milne-Edwards, Lamarck's Anim. sans 

 Vert., 2nd ed., 1836, p. 154. 



Dynamena operculata, Lamouroux, Hist. Pol. Cor. Flex., 

 1816, p. 176 ; Id., Lamouroux, Expos. Meth., 1821, 

 p. 12. Id., Blainville, Man. d'Act., 1834, p. 483, pi. 

 83, fig. 5, 5a. Id., Esper, Die Pflanz., 1788-1830, iii., 

 p. 191. Id., Krauss, Cor. und Zooph. der Siidsee, 1837, 

 p. 27. 



Amphisbetia operculata, L. Agassiz, Cont. Nat. Hist. U.S., 

 iv., 1862, p. 355. 



Dynamena fasciculata, Kirchenpauer, Verhandl. der K. 

 L.-C. d. Akad., xxxi., 1864, pp. 8, 12, fig. 7. 



Odontotheca operculata, Levinsen, Vidensk. Medd. fra den 

 naturh. Foren, 64, 1913, p. 308. 



? Dynamena pulchella, D'Orbigny, Voy. Amer. Merid., v., 5, 

 Zooph., 1839-1846, p. 26, pi. xi., figs. 9-11. 



? Sertularia pulchella, Nutting, Amer. Hydr., Sert., 1904, 

 pi. ii., fig. 6 (not fig. 7) after D'Orbigny. Id., Hart- 

 laub, Zool. Jahrb., Suppl. vi., iii., 1905, p. 667, figs. 

 B 5 , C 5 after D'Orbigny. 



? Sertularia crinis, Allman, Journ. Linn. Soc., Zool., xix., 

 1885, p. 139, pi. xiv., figs. 1, 2. 



The specimens belong to the bidentate form, which I cannot 

 but regard as typical, for although Johnston and Hincks 

 concur in describing the species as possessing normally one 

 long tooth on the hydrotheca-margin, with a minute denticle 

 on each side of it, observers generally mention only the biden- 

 tate form, and I have myself seen no other. 



Excepting the closely allied 8. bispinosa and S. trispinosa, 

 and one or two doubtful forms, I know of no other species of 

 Sertularia quite like the present in habit. Though branching 

 profusely, there is no distinction of stem and branches ; all 

 the divisions are alike, the ramification is strictly dichoto- 

 mous, and the two members of each bifurcation are about 

 equal, and are in divergent planes. The gonangia are rather 

 narrow in proportion to their length, and I have never seen 

 them compressed and widened upwards like those of S. 

 bispinosa. 



Sertularia usneoides, Pallas, has long been recognised as 

 identical with 8. operculata, while 8. serra, Lamarck, and 

 Dynamena brevicella, Lamouroux, are included among the 

 synonyms on the authority of Billard, who has examined the 

 types. Kirchenpauer's Dynamena fasciculata also is obviously 

 no other than the present species. 



