AMERICAN HYDROIDS. 



107 



regard the gonosonie as a true corbula. Bale took exception to this, wisely I think, and included 

 these species in the genus Aglaophenia, regarding their gonosomes as true corbuhe. While agree- 

 ing fully with the latter author, the present writer considers that the presence of hydrothecre on 

 the corbula leaves is a good generic distinction, upon which, in connection with the stem character 

 and certain features of the hydrothec;e named above, he has ventured to establish the new genus 

 Tliecocarpus, which would equal a part of the subgenus Lytocarpia Kircheupauer, part of the genus 

 Lytocarpus of Allman, or a part of the genus Aglaophen-ia as defined by Bale. 1 



2 mesial nematophores . 



1 mesial uematophore. 



KEY TO AMERICAN SPECIES OF THE GENUS THECOCARPUS. 



Hydrotheca; separated by more than half their height, narrowed below. 



T. bispinosiis. 

 Hydrothecai separated by more than half their height, not appreciably 



narrowed below T. benedicti. 



Hydrothecir separated by more than half their height, narrow below. 



T. distans. 

 Hydrotheca? closely approximated, no conspicuous internal thickening 



of intemode behind hydrotheca T. normani. 



Hydrotheea; closely approximated, thickenings of internodes evident. 



T. myriophyllum. 



Distribution of American species of the genus Thecocarpus. 



THECOCARPUS MYRIOPHYLLUM (Linnseus). 

 (Plate XXIV, figs. 12, 13.) 



Sertiilaria myriophyllum LINN.EUS, Syst. Nat., 1767, p. 1309. 



SertuJaria myriophyllum PALLAS, Eleuchus Zooph., 1766, p. 153. 



Ai/laoplieniu myriojilii/llum LAMOUROUX, Polyp. Cor. flex., 1816, p. 168. 



Plumularia myriophyllum LAMARCK, Anim. sans Vert., 1836, 3d ed., II, p. 159. 



Pliimularia myriopliyllum JOHNSTON, Brit. Zooph., 1847, p. 99. 



Plumularia myriophyllum LANDSBOROUGH, Pop. Hist. Brit. Zool., 1852, p. 15^. 



Aglaophenia myriophyllum Louis AGASSIZ, Cont. Nat. Hist. U. S., 1862, IV, p. 358. 



Aylaophenia myriophyllum HlNCKS, Brit. Hydroid Zooph., 1868, p. 290. 



Aijlaoplienia myriophyllum KIRCHENPAUER, Hydroidenfam. Plnmularida>, 1872, Pt. 1, p. 28. 



Lytocurpus myriophylliim ALLMAN, Challenger Report. Plumularidie, 1883, p. 40. 



Lytocarpns myrioplii/llum PENNIKGTON, Brit. Zoophytes, 1885, p. 130. 



Lutoearpus myriophyllum MARKTANNER-TuRNERETsCHER, Die Hydroiden des k. k. uaturhist. Hofmuseums, 1890, p. 277 



Trophosome. Colony unbranched, or sparingly branched, attaining a height of 18 inches; 

 stem fascicled, with flattened protuberances formed by the contortion of the component tubes; 

 hydrocladia alternate, close set, divided into regular iutemodes, each of which bears a hydrotheca. 

 Hydrothecib stout, cylindrical, with a median anterior tooth, and lateral sinuatious; there are 

 well-marked internal ridges on the side of the internode nearest the hydrotheca, and the iutrathecal 

 ridge is more evident than usual in this genus; supracalyciue ueiuatophores small, slightly over- 

 topping the hydrotheca; mesial nematophore adnate to the front of the hydrotheca, and attaining 

 the level of the iutrathecal ridge; numerous small or rudimentary cauliue nematophores on the 

 tubes composing the stem. 



1 Genera of the Plumulariidse, pp. 12, 14. 



