38o 



BUI<I.ETIN OF THE BUREAU OF FISHERIES. 

 Genus MONOST^CHAS. 



Trophosome. — Colony dichotomously branched; hydrocladia all springing from the upper side of 

 the branches; cauline nematophores absent. 



Gonosome. — Gonangia without special protection; oval or ovate. 



I Monostxchas quadridens (McCrady). 



Plumularia quadridens McCrady, Proc. Elliott Soc, 1857, p. 97. 

 MonostcEchas quadridens. Nutting, American Hydroids, pt. I, 1900, p. 75. 



Trophosome. — Colony attaining a height of 6 inches, dichotomously 

 branched; branches coming off from the main stem at irregular inter- 

 vals; branches divided into long intemodes, each intemode giving rise 

 to a hydrocladium from its upper side and distal end; several long, 

 slender nematophores are present on the upper side of each intemode. 

 The hydrocladia are given off at such an angle that they all pass up in 

 the same general direction as the main stem and hence run parallel to 

 one another. Each hydrocladium is divided into alternate hydrothecate 

 and intermediate intemodes, the proximal one being hydrothecate. 

 Each hydrothecate intemode is oblique proximally and straight dis- 

 tally, each intermediate, straight proximally and oblique distally. 

 HydrothecEe large, campanulate; supracalycine nematophores, borne 

 on distinct intemodal processes, reach to or above the margin of the 

 hydrotliecae; mesial nematophore present; one or two nematophores to 

 each intermediate intemode. 



Gonosome. — Gonangia oval to spherical, borne on a process imme- 



FiG. 46. — Monosiackas quadridens diately below the hydrotheca, often occurring in series, one for each 

 (McCrady). hydrotheca for some distance along the hydrocladium. Each gonangium 



is provided with a pair of nematophores at the base. 



Distribution. — On sponge dredged by the Fish Hawk. 



Genus MONOTHECA. 



Trophosome. — Stem usually unbranched; hydrocladium consisting of a 

 proximal nonhydrothecate and a distal hydrothecate intemode. The latter 

 is terminated by a pair of nematophores. 



Gonosome. — "Gonangia borne on the stem, usually on the proximal 

 portion , ovate or sac-shaped and without protective appendages. " — Nutting. 



Monotheca margaretta Nuttmg. 



Mcmotheca margaretta Nutting, American Hydroids, pt. I, 1900, p. 72. 



Trophosome. — Colony reaching a height of nearly half an inch, usually 

 unbranched; stem divided into regular intemodes by a double annulation, 

 the portion between the rings being of less diameter than the remainder of 

 the stem, regularly geniculate so that it looks like Obelia gcniculata in 

 miniature. A hydrocladium is given off at the distal end of each intemode. 

 The proximal intemode of each hydrocladium, which is nonhydrothecate, 

 is connected with the stem by a joint, similar to those on the stem. The 

 distal intemode (tliere are but two) is curved to support the hydrotheca and is bifid at the extremity, 

 each portion of the fork having a nematophore; these would correspond to the regular supracalycine 



Fig. 47. — Monotheca margaretta 

 Nutting. A, portion of colony; 

 B and C, hydrothecae. 



