40 



VERRILL ON THE POLYPS OF THE 



Astrangia Danse Agassiz. 



Astrangia Dance Agassiz, Proc. Amer. Association, ii. p. 68, 1849 (non M.-Ed\v. and Haime). Astrangia astreiformis Leidt, 

 Journal Acad. Nat. Sci. Philadelphia, 2d series, iii. p. 135, 1855 {non M.-Edw. and Haime). 



In its mode of growth and general form this species resembles the preceding, but does 

 not form so thick masses and the corallites are less closely united. Their walls are 

 smoother, with less distinct costae. The cells are not so deep and have a more open ap- 

 pearance, owing both to the much less developed columella, which is, however, more dis- 

 tinct from the septa and composed of larger papillae, and to the narrower septa of the 

 fourth cycle, which do not extend half-way to the centre. The polyps are very exsert in 

 expansion, with about twenty-four long slender tentacles. The disk is usually convex or 

 conical. Color of polyps white or light flesh-color, diaphanous. (Coll. Mus. Comp. Zool.) 



Long Island Sound. 



This species incrusts rocks from just below low-water mark to ten fathoms, and is very 

 abundant in some localities. It thrives well in the aquarium, eating oysters and other 

 mollusca with avidity. 



Prof Agassiz has an excellent series of unpublished plates, representing the polyps of 

 this species in various attitudes, with the details of its anatomy. 



Family Oculinid^ Milne-Edwards and Haime. 



Genus Oculina Lamarck. 



The corallum while young spreads laterally by basal budding, forming an incrusting 

 base, from which branches arise in a tufted or arborescent manner. Corallites arranged 

 somewhat spirally on the branches, separated by a compact coenenchyma, the surface of 

 which is nearly smooth midway between the cells, but marked by radiating costae near 

 them. These are rather deep, with a papillose columella and pali before all the septa 

 except those of the last cycle. Edges of the septa entire or nearly so, moderately 

 exsert. 



Oculina arbuseula Agassiz. 



In this species the corallum is arborescently branched from near the base, which is 

 spreading and incrusting. The trunk is short, very thick, and divides soon into 

 several large diverging branches. These are round, usually somewhat bent, gradually 

 tapering, and very rapidly divide dichotomously into two or three spreading branchlets, 

 which are curved and taper rapidly to the blunt tips. Corallites a little prominent, gen- 

 erally with perpendicular walls, arranged spirally around the branches, not crowded ; cells 

 rather large, and deep. Septa in four cycles, those of the last generally incomplete. The 

 principal ones are narrow, nearly perpendicular within, their summits somewhat exsert, 

 rounded. Columella slightly developed, pali rudimentary or but slightly prominent. Cos- 

 tae distinct only near the cells ; surface of the coenenchyma finely granulous, often convex 

 between the cells. Unbleached specimens are light yellowish brown. In a specimen eight 

 inches high the principal branches are .75 of an inch in diameter ; the cells about .12. 



Charleston, S. C, off the bar, L. Agassiz. (Coll. Mus. Comp. Zool.) 



