MUSEUM OF COxMPAllATIVE ZOOLOGY. 73 



CALYPTOBLASTEA. 



/■ 



CAMPANULARIAD^. 

 Obelia castellata, sp. nov. 



Plates I., II., Figs. 3 to 9 inclusive. 



Trophosome. A small specimen a trifle over three eighths of an inch in length 

 is all that was found. As there was no hydrorhiza, and as the stem at the base 

 is broken, it is quite possible that this may be but a fragment of a colony. It 

 looks much like a branch of 0. gelatiiiosa, in which the entire colony is often 

 six inches long. 



The stem is monosiphonic, enlarged at each node, with three or four annu- 

 lations immediately above each node; the direction of the stem changes at the 

 nodes, alternately to the right and left. 



The branches are arranged alternately, and are like the stem in the several 

 characters mentioned. 



The hydrothecce are rather deeply campanulate, with a castellate margin : 

 they are borne on pedicels, usually annulated throughout, and generally consist- 

 ing of eight to twelve annulations ; the number varies, however, occasionally, 

 from four or five to eight ; the pedicels at the ends of branches are annulated 

 at both extremities and smooth between ; the hydrothecoe occur also at the 

 axilla3 between the branches and stem, and between the branchlets and 

 branches. I was unable to satisfy myself about the existence of a floor or 

 internal partition near the base ; something of that nature appears in two 

 hydrothecse, but not in any of the others (see Plate T. Fig. 5). The specimen is 

 considerably battered, most of the hydrothecse being wrinkled, and the caeno- 

 sarc is gone. 



Gonosome. There are four Gonangia occupying axillary positions on the 

 main stem, which position each one shares with the peduncle of a hydrotheca ; 

 they are obovate, with a terminal, circular aperture, with one or two faint 

 annulations toward the distal end, and borne on short pedicels of three to five 

 annulations. 



Locality. Station 3357. About 140 miles southwest of the city of Panama. 

 Bathymetrical record, 782 fathoms. 



This form is allied to Obelia gelatinosa, from which it differs in the struc- 

 ture of the Gonangia (see Plate I. Figs. 7, 8, and Plate II. Fig. 9). Should 

 there prove to be no bottom or floor to the hydrothecte in this form, that 

 would be another distinction between castellata and gelatinosa. Further, if 

 this is only a branch, and the main stem is polysiphonic, that is an important 

 similarity between the two ; while if it retains the monosiphonic character, it 

 emphasizes the distinction between these species. 



