72 AMERICAN HYDROIDS. 



pinuately along a considerable portion of the stem, but thoy are always irregularly distributed 

 in the distal part of the colony. A verticillate arrangement is not apparent in any of the 

 specimens at hand, which might easily be mistaken for a species of Phtmularia , so pronounced is 

 the pinnate arrangement of the hydrocladia. 



Type slide*. Cat. Nos. 18633, 18G34, U.S.N.M. ; Oat. Nos. 15320, 15321, Mus. State Univ. Iowa; 

 also in the collection of the author. 



MONOTHECA, new genus. 

 Monopyjris KiRCHENPAUER, Ueber die Hydroidenlamilic Pluinnlariibc, 1876, Pt. 2, pp. 17, 21. 



Trophosome. Stem simple or sparsely branching, divided into intercedes; hydrocladia bear- 

 ing each a single hydrotheca and consisting of two internodes, of which the distal one bears the 

 hydrotheca and supports two supracalyciue uematophores on an enlargement or a bifurcation of 

 its distal eud. 



Gonoxome. Gonangia borne on the stem, usually on the proximal portion, ovate or sac shaped, 

 and without protective appendages. 



Kirchenpauer, in his work on the IMumularida- referred to above, divided the old genus 

 Phimularia into three subgenera, which he called "Isicoki, n " Anisocola," and " Monopyxis." 

 The first and second of those were based upon characters which are of little systematic impor- 

 tance, that is, the possession or absence of intermediate internodes on the hydrocladia. The 

 third subgenus, Monopya-ix, as Bale justly remarks, "is founded on a more valid distinction," 1 

 the possession of a single hydrotheca to each hydrocladium. It therefore seems convenient and 

 proper to raise the subgeuus to generic rank. The name Monopy.ris, however, was preoccupied 

 by Ehrenberg in 1834. I therefore propose the name Monotheca as the generic appellation of 

 the group. 



MONOTHECA MARGARETTA, new species. 

 (Plate XI, figs. 1-3.) 



Trophosome. Colony attaining a height of about one-fourth of an inch, usually unbranched, but 

 occasionally sending off a single lateral branch, stem not fascicled, divided regularly into internodes, 

 each of which bears a hydrocladium on a process from its distal end, and plainly geniculate, there 

 being a bend opposite the origin of each hydrocladium; hydrocladia consisting of a proximal 

 short iuteruode bearing neither hydrotheca nor nematophore, and a distal longer internode bearing 

 a hydrotheca and bifurcating at its distal end, thus furnishing supports for the two supracalycine 

 uematophores. Hydrotheca- conical, rather deep, margin circular and entire; supracalycine 

 neinatophores overtopping the hydrotheca and borne on the forked ends of the hydrocladia; a 

 mesial nematophore at the base of each hydrotheca, two to four uematophores in the axil of each 

 hydrocladium, and one cauliue ueuiatophore to each internode of the stem. 



Gonosome. Xot known. 



Distribution. Shallow water, near Little Cat Island, Bahamas. State University of Iowa 

 expedition. Found attached to alga 1 . 



This is an exceedingly delicate and graceful species, which is affectionately dedicated to the 

 author's mother. It may be readily distinguished from its nearest allies by the distinctly forked 

 condition of the distal ends of the hydrocladia. 



Type slides. Gat. Nos. 11715, 11716, Mus. State Univ. Iowa; Cat. Nos. 18015, 18G16,U.S.N.M.; 

 also in the collection of the author. 



ANTENNOPSIS Allman (modified). 

 Antennopsis ALLMAN, Mem. Mus. Couip. Zool., 1877, V, No. 2, p. 34. 



Trophosome. Stem jointed; cfeuosarc not canaliculated; hydrocladia scattered irregularly 

 over the stem, sometimes approaching a verticillate arrangement. 



Oonosome. Gonaugia borne in the axils of the hydrocladia, without protective appendages. 



1 Australian Hydroid Zoophytes, 1881, p. 123 



