1S81.] NATURAL SCIENCES OF PHILADELPHIA. 345 



arrangement of the arms, in their greater length, depressed 

 spatulate form ; also in the form of the cal^^x, the extended basal 

 ring, the preponderance of the dome portions over the calyx, the 

 excentric position of the anal tube, its inflated character, and its 

 /disposition to bend sideways. We consider these characters 

 sufficient for a full generic division, and propose the following : — 



Revised Generic Diagnosis. — Body small, biturbinate or sub- 

 globose ; calyx truncate at the base, composed of smooth, convex 

 or nodose plates with rarely striatious. Vault more or less inflated, 

 and exceeding the calyx in its dimensions. 



Basals three, equal, formed into a wide rim, which extends far 

 bej^ond the periphery of the column. Primary radials 3X5; the 

 first large, equal in size to the second and third together, and 

 wider than either of them ; the second quadrangular ; the third 

 regularly pentagonal, sometimes smaller than the second. Sec- 

 ondar}" radials composed of two series of plates each, and so are 

 the tertiary radials when present. The plates of the marginal 

 row, those supporting the arms, form a projecting circlet around 

 the body, and are laterally extended ; they are large, their outer 

 sides excavated for the reception of the arm plates, the upper side 

 notched for the ambulacral passages. At the side of the arm 

 openings, which are generally directed obliquely toward the vault 

 and close to the arm, there is located a respiratory (?) pore, which 

 is arranged like in Batocrinus, and generally as large. The arm 

 openings are arranged in groups of two, three, four, or five each, 

 with great variability' in the difierent raj^s. There are from twelve 

 to twenty-two arm openings in all, and each one supports either a 

 simple or a compound arm. The openings of adjacent raj'S are 

 placed farther apart than those of the same ra}^, and are separated 

 by a small depression, which at the posterior side of the body is 

 considerably deeper and wider. 



Arms fully twice as long as in Batocrinus, the upper portions 

 flattened, much wider, and folded inward. They are composed of 

 a double series of joints, which at the bottom rest upon one or 

 two small cuneate pieces. The succeeding arm plates are generally 

 short, but they become gradually longer as they increase in width. 

 The lower portions of the arms are round or nearly so, the 

 increase in width beginning at one-fourth to one-third their 

 height, vfhen they are gradually flattened, spread out laterally, 

 and become broad and spatulate, remaining thick and heavy along 



