ACTmOCEINIDJE. 555 



radials, first costals and anal plate are transversely elongate, and occupy 

 nearly one fourth the surface of the plates ; while those upon the inter- 

 brachials, which have a circular outline, are proportionally smaller. There 

 are generally three ridges between the radials, basals and costals, but these 

 are not continuous, extending only to the margins of the nodes; two proceed 

 to the first interbrachials, while the other plates up to the brachial extensions 

 are connected by single rows. Suture lines distinct. 



Basals large, forming a broad and deep cup, which at its lower margin is 

 distinctly notched; the lower edges of the plates expnnding, and forming 

 a smooth, thickened, trilobate rim, which stands out conspicuously from the 

 column. Eadials as wide as long — in very large specimens proiDortionally 

 longer — more than twice as large as both costals together ; the lateral 

 faces longer than the sloping upper ones. First costals nearly as wide as 

 long, and hexangular ; the second very short, sometimes less than half the 

 length of the first, and obliquely angular above. Distichals small, all axil- 

 lary, giving off from one side an arm, which is free and biserial from the 

 second plate, and generally simple throughout : from the other side three 

 palmars, which support two arms, which both bifurcate once or twice in their 

 free state at some distance from the calyx. Arms long, moderately heavy, 

 rounded on the back, and nearly as thick at the distal end as at the proximal. 

 Arm joints short and slightly convex. Piimules rather thin, and only their 

 three or four proximal joints are provided with small hooks. Interbrachials: 

 1, 2, 3, followed by a number of others in the equatorial region; the first as 

 large as the first costals, those of the second and third rows smaller. Anal 

 plate somewhat shorter than the radials ; supporting two plates in the first, 

 three in the second, and four to five in the third row. Tegmen composed 

 of slightly convex, moderately large pieces. Orals in contact, the posterior 

 one small and placed transversely ; the others larger than any of the sur- 

 rounding plates, but otherwise not distinct; they are elongate, and narrowest 

 at the lower end, leaving notches, which enclo.se the first radial dome jjlate. 

 The latter is followed by two plates of a second order, and these by alternate 

 rows of minute covering pieces. Anal tube extremely long, extending far 

 out above the tips of the arms, and heavy throughout ; the plates strongly 

 tuberculous and sharply pointed at the top, some of them larger and sub- 

 spmous. Column large at the upper end, but tapering distinctly downward. 

 The nodal joints near the calyx con.siderably longer and wider than the 

 intervening ones, and angular at the edge,s, but gradually with their decrea.se 



