476 PROCEEDINGS OF THE AMERICAN ACADEMY. 



phore in any way similar to this. It falls in a natural group with the 

 other species here described, H. beanii, H. dichotomum, H. sessile, and 

 H. hermudense, because all have large hydranths, shallow hydrophores, 

 and slipper-shaped female gonothecae. It is of interest for purposes of 

 comparison to arrange the salient characters of the female gonophores 

 of these forms in an order suggested by their structure. 



H. mark}. Female gonotheca has two tubes, each bearing a hy- 

 dranth, which reach from the centre of the gonophore to its summit. 

 The opening is at the summit. 



H. beanii. Tubes much shortened and mouth at top on a level with 

 the tubes. 



H. dichotomum. Only one tube springing from the side half-way 

 down. 



H. sessile. Like H. bermudense, but the opening at top and the 

 remains of tube gone. 



Though recognizing that caution should be used in formulating theo- 

 ries as to the development of animal structures from such comparisons 

 as are suggested above, it seems to me that the facts point forcibly to 

 the origin of the slipper- shaped gonotheca in the following way. The 

 gonotheca structure in the present species suggests that a hydrophore 

 bearing a gonotheca also gave rise to a branch on either side, the latter 

 a common condition in the species. The two branches with their ter- 

 minal hydranths then became fused with the gonotheca. In this 

 species the fusion is complete half-way up the gonotheca. Next the 

 tubes shortened further by a contraction of their upper part until they 

 became mere openings and the aperture of the gonotheca remained 

 near to them, as in H. macrocephalum. In H. bermudense the opening 

 is elongated toward the top. H. sessile and others have the opening 

 at the top, but retain the slipper-like form. 



Genos SERTULARELLA Gray (modified), 1847. 



Sertularella speciosa (new species). Figures 24-28. 



This form was found only at the opening of an underground passage 

 connecting Harrington Sound and Castle Harbor (lat. 32° 20' 30", 

 long. 64°42' lO"). 



Trophosome. Colonies fascicled, truncate, usually five to eight inches 

 high (Figures 24, 28). Occasionally a large branch occurs resembling 

 the main colony. Pinnae alternate, making an angle of eighty degrees 

 with the stem, divided into nodes at intervals of some five hydrothecae 

 by grooves slanting alternately in opposite directions. Stolons occur 

 at ends of stems and branches. 



