POLYPS AND CORALS. 91 



twelve very narrow, rudimentary septa, six of which can 

 usually be traced across the bottom of the cell to the 

 columella. Spaces between the cells usually less than 

 their diameter. Surface of the ccenenchyma covered with 

 very small, scattered, rough points. Color of unbleached 

 coral light brownish yellow. Height 2.5 inches ; breadth 

 about the same ; diameter of the main branches .25 of an 

 inch. 



Loo Choo Islands. Dr. Wm. Stimpson. 



This species is allied to P. ccespitosa Dana, from the 

 Sandwich Islands, but the latter has larger cells, which 

 are much more closely crowded near the ends of the 

 branchlets, leaving onl}^ a thin wall between, therefore 

 becoming polygonal, and the columella is not distinct. 

 The terminal branchlets are also more angular and 

 pointed, more irregular, and have the cells opening 

 obliquely upward. P. bulbosa Lam. has much longer 

 and stouter branches, which are less subdivided and 

 more angular at the ends. Its cells are still larger and 

 towards the ends of the branches they are oblong-polyg- 

 onal, with only- thin walls between them, and open 

 obliquely upward. 



PociLLiPOEA c^sPiTOSA Dana. 



Pocillopora brevicornis (pars) Dana; Edw. andHaime (no)i Lamarck). 



The Museum of Yale College possesses a large and fine 

 series of this species from the Hawaiian Islands, collected 

 by Mr. Horace Mann, and also several of the original 

 specimens described by Prof. Dana. One specimen from 

 the U. S. Exploring Expedition, labelled P. brevicornis 

 by Dana, difiers from the ordinary form in having the 

 branches shorter and thicker, with the branchlets shorter 

 and more crowded upon their enlarged ends, thus pro- 

 ducing a thicker and lower clump than usual. But in the 

 series there are various intermediate forms between this 

 and those with long branches and slender spreading 

 branchlets. Like most specimens of this species from the 

 Hawaiian Islands, it has the large, flat, open bulbs made 

 among its branches by Harpalocarcinus marsupialis Stimp- 



