THE CAMPANULAKIDiE AND THE BONNEVIELLID^. 83 



Distribution. — This species, like the last, has a very extensive distribution, having been re- 

 ported by many writere from the British Isles, Scandinavia, the Arctic Sea, North Sea, coasts 

 of France, Mediterranean and Adriatic Sea. 



It is mentioned by several writers as found on our New England coast, but it is not Imown 

 from the southern United States or West Indian region. In the Pacific it has been reported from 

 Alaska to San Diego, in southern California. Hartlaub (1905, p. 580) reports this species from 

 St. Paul Island, regarding Ohelia australis von Lendenfeld as a synonym of 0. dichotoma. If he is 

 correct in this decision, the range of the species must be extended to New Zealand. The present 

 writer, however, does not feel at all certain of the identity of 0. australis and 0. dichotoma. 



A specimen without gonosome but apparently of this species was secured by the Alba- 

 tross at station 3531, off San Francisco, CaUfornia, at a depth of 59 fathoms, and Billard reports 

 it from the Gulf of Cadiz at a depth of 65 fathoms. 



OBELIA COMMISSDRALIS McCrady. 



Plate 21, figs. 1-5. 



Ohelia commissuralis McCrady, Gymnopthalmata of Charleston Harbor, 1859, p. 95. 



Ohelia commissuralis L. Agassiz, Cont. Nat. Hist. U. S., vol. 4, 1862, p. 315. 



Ohelia commissuralis A. Agassiz, The Acalephan fauna of the southern coast of Mass., Proc. Best. Soc. Nat. Hist., vol. 



8, 1862, p. 225. 

 Ohelia commissuralis Allman, Construction and Limitation of Genera, Ann. Mag. Nat. Hist., ser. 3, vol. 13, 1864, p. 372. 

 Ohelia commissuralis A. Agassiz, On the mode of development of the marginal tentacles of the free medusae of some 



Hydroids, Proc. Best. Soc. Nat. Hist., vol. 9, 1865, p. 91. 

 Qhelia commissuralis A. Agassiz, North Amer. Acalephae, 1865, p. 86. 

 Ohelia commissuralis Vereill, Invertebrate Animals of Vineyard Sound, 1873, p. 728. 

 Ohelia commissuralis Brooks, Studies Biol. Lab. Johns Hopkins Univ., vol. 2, 1882, p. 176. 

 Ohelia commissuralis Fewkes, Embryological monographs, III, Acalephse, Mem. Mus. Comp. Zool., vol. 9, 1884, pi. 3, 



figs. 1-5. 

 Ohelia commissuralis Hargitt, Synopsis N. A. Invert., Amer. Nat., 1901, p. 382. 

 Ohelia commissuralis Nutiing, Hydroids of the Woods Hole Region, 1901, p. 382. 

 Ohelia commissuralis Torrey, Hydroida of the Pacific Coast, 1902, p. 56. 

 Ohelia coinmissuralis Haegitt, Medusae of the Woods Hole Region, 1905, p. 48. 

 Ohelia commissuralis Mayer, Medusae of the World, vol. 2, Hydromedusae, 1910, p. 244. 

 Ohelia commissuralis Frasee, West Coast Hydroids, 1911, p. 38. 



TropJiosome.'- — Colony 9.5 cm. high, consisting of a simple slender stem, from which numer- 

 ous compound branches are given off on all sides, forming a beautiful, profusely branched 

 colony. The main branches are branched, often dichotomously, several times and bear groups 

 of amiulations above each branch or pedicel origin. The pedicels are alternate and, as described 

 by Mayer, "arise simply, not from distinct swollen, shoulder-hke enlargements of the stem." 

 They are often but not always shorter than the hydrothecse and are usually annulated through- 

 out, but sometimes have a median bare portion. The hydrothecse are deeply campanulate, with 

 an even rim and well-marked diaphragm. The polyps in this specimen are beautifully expanded 

 and show 24-30 tentacles and a pyriform proboscis. 



Gonosome.— The gonangia are borne ia or near the axils of branches and pedicels. They 

 are oblong-ovate in shape, with a distinct distal shoulder and narrow collar surroutnding the 

 disk-shaped operculum. They are borne on short annulated pedicels and contain developing 

 medusae. "When set free the young medusa usually has 16 tentacles and no trace of gonads" 

 (Mayer). 



Distribution. — Type-locahty, Charleston Harbor. The species is common on the Atlantic 

 coast of United States north of this point. It has also been reported by Torrey from San 

 Francisco, California. This species is carefully described and figured by L. Agassiz.^ 



Bathymetric distribution, 1 to 10 fathoms (?). 



'Description of a colony collected by Mr. George Gray, at Woods Hole, Massachusetts. 

 2 Cont. Nat. Hist. U. S., vol. 4, p. 315, pis. 33, 34. 



