128 THE PLUMULAKID.K. 



on the remaining portions, divided into regular internodes without septal ridges. Hydrothecae 

 quite variable iu colonies of different ages, usually rather deep, axis of aperture inclined at 

 an angle of 45 degrees with that of tlie hydrocladium; three lobate teeth on each side of the 

 margin; a strong anterior fold or llexure aud an anterior ridge reaching the middle of the 

 bydrotheca, aud turned upward at its distal end; supracalycine nematophores small, short, 

 not reachiug the top of the hydrotheca; mesial nematophores exceedingly variable, consisting 

 of a mere spur at the base of the hydrotheca in the very young colony, and increasing iu 

 size until the distal end considerably overlaps the hydrotheca in fully developed colonies; 

 caiiline uematophores bilobate, very large, two at the base of each hydroeladium. These also 

 vary in size with the size of the colony. 



Gonosome. Gouaugia almost hemispherical, the distal ends being very broad and perfectly 

 flat, borne singly at the bases of the hydrocladia. No protective appendages of any kind. 



Distribution. Shallow water between Eleuthera and Little Cat Island, Bahamas; State 

 University of Iowa Expedition. 



This species begins life as a parasite on Lijtociirju/n clrkri, to which it attaches itself by 

 a creeping root-stalk. The very young colony takes the shape of a single hydroeladium, stand- 

 ing erect from this root-stalk. Later the hydrocladiiim seems to send oft' lateral hydrocladia, 

 itself becoming a stem without hydrotheca'. How this transformation takes place is not shown 

 by my specimens, and 1 am not sure that I have rightly interpreted the process. I5oth single 

 hydrocladia and sterns giving forth regular hydrocladia grow from the same creeping root- 

 stalk. 



At certain stages the hydrotheca' of this species greatly resemble those of If. spcciona. 

 The bilobate and very large cauline nematophores constitute a good feature by which 

 H. rariabilis may be identified. 



Type sliflcx.Uiit. Nos. 15107, 1540.S, Mus. State Univ. Iowa; Cat. Nos. 18705, ISTOli, 18707, 

 U.S.N.M.; also in the collection of the author. 



NUDITHECA, new genus. 



Tropliosomr. Stem fascicled; hydrocladia compound, or branched; supracalycine and mesial 

 nematophores present; hydrothecal margin without teeth. 



Gonosomc. Gouaugia borne singly on the hydrocladia, and devoid of phylactogonia, but with 

 two or three nematophores on their pedicels. 



This genus is based on a remarkable species described by S. F. Clark 1 in 1*76. The unusual 

 features of this species seem to have escaped the attention of the leading workers in Hydroids, 

 as no mention of it is made in any of the more comprehensive works since its original description 

 twenty years ago. 



The compound hydrocladia, each branch of which bears numerous hydrotheca', is a feature 

 not elsewhere found among the Statoplea. These subdivisions of the hydrocladia must not be 

 confounded with the various accessory ramtili, phylactogonia, etc., for the protection of the 

 gonangia. They arc, on the contrary, genuine, unmodified hydrocladia. The position of the 

 gonangia is similar to that found iu Halicornnria n/n-i-nria Allman, with this difference, liowever, 

 that in the latter species the gouangium manifestly takes the place of a hydrotheca, while in 

 XmlitlH'nt no hydrotheca is wanting, the gonangium being interposed between a mesial nemato- 

 phore and the hydrotheca behind it. Iu other words, the gonangium does not seem to be the 

 homologue either of a liydrotlieca or a nematophore. 



This genus has strong affinities with the Eleutheropleau group. The uematophores are 

 expanded above, and bithalamic, although strictly " fixed." Moreover, branched hydrocladia are 

 found only iu that group. The two or three uematophores at the base of the unprotected gouau- 

 giurn also remind one forcibly of numerous similar arrangements among the Eleutheroplea. 



1 Proceedings of the Academy of Natural Sciences oi' Philadelphia, 1876, p. 230. 



