Collected by the late Dr. J. I. Northrop. 193 



forms a ring around its base (i. e., its mouth), so that when con- 

 traction takes place the base of the cavity is drawn up like a purse 

 and the body wall bulges out and forms a tubercle." 



The upper portion of the column, which, in completely con- 

 tracted individuals, forms the apex, is destitute of tubercles and 

 is furnished with numerous longitudinal ridges. The sphincter 

 muscle is strong and has the form represented in fig. 8, being 

 simple, though showing a tendency to be divided into two parts, 

 an evident constriction (cr) occurring upon it. This is not an in- 

 dividual peculiarity, as I have found it in three individuals ex- 

 amined, and it is interesting as forming an intermediate condition 

 between the simple sphincter of 1. tuberculatum and the double 

 one of the genus Zoanthus. 



The tentacles are arranged in two rows and their number seems 

 to be double that of the pairs of mesenteries. 



The mesenteries are arranged on the microtype, and vary in 

 number in the different individuals from eighteen to twenty-three 

 pairs. They are much more slender than those of /. tuber culatus, 

 and though thickened towards their insertion with the column 

 wall, yet this thickening is slight when compared with that of 

 tuberculatus. Two or three slightly elongated (in section) canals 

 are found in the thickened portion of the perfect mesenteries, the 

 imperfect ones containing but one canal. I^o reproductive organs 

 occurred in any of the specimens examined. 



The stomatodseum presents a well developed siphon oglyphe and 

 its surface is thrown into numerous marked ridges which corre- 

 spond in a general way, but not accurately, with the intervals be- 

 tween successive pairs of perfect mesenteries. 



LIST OF KEFEEENCES. 



1886. Ellis, J. — The Natural History of many curious and uncommon Zoo- 

 phytes collected from various parts of the Globe systematically ar- 

 ranged and described by Daniel Solander. London. 1786. 



1817. Lesueue, C. a. — Observations on several species of the genus Actinia ; 

 illustrated by figures. — Journ. Acad. Nat. Sci. Philadelphia. Vol. I. 

 1817. 



1828. Geay, J. E. — Spicilegia Zoologica. London. 1828. 



1850. DucHASSAiNG, P. — Animaux radiaires des Antilles. Paris. 1850. 



1860. DucHASSAiNG, P. ET MiCHELOTTi, G.— Memoire sur lesCoralliaires des 

 Antilles— ifem. de VAcad. Sci. Turin. Ser. IL Tome XIX. 1860. 



