Description of Two New Genera and Eight New Species. 35 



each series before the two arms become free. The first one has a 

 length equal to that of the third primary radial, but the succeeding 

 plates are shorter, without an}' determined contraction in width, and 

 graduate up to the cuneiform plates that form the free arms. Were 

 the other radial series like this one, wo would have a species with only 

 ten arms, but such is not the case. In the other series, in our speci- 

 men (that upon the left) there are three secondary radials, each of 

 which has a length about equal to the third primary radials. Upon 

 the upper sloping sides of the third secondary radials arise tertiary 

 radials, the first of which has a length nearly equal to that of a second- 

 ary radial. The succeeding plates are shorter and seem to graduate 

 into the cuneiform plates of the free arms at about the sixth plate. 

 Here are four arms to this radial series or twice as many as there are 

 in the first described series. We are not prepared to call this anomal- 

 ous arrangement abnormal, for the specimen is well developed, and the 

 arms well preserved and the species quite distinct in other respects 

 from any hitherto described. 



Interradial and inter secondary radial areas. — These areas are de- 

 pressed. The first plate rests between the upper sloping sides of the 

 first primary radials, this is followed by a range of two plates, and 

 these again by a range of two, and these by a third series before pass- 

 ing the top of the third primary radials. Above this, plates continue 

 to fill the narrow interradial space to the top of the calyx, but neither 

 their number nor arrangement has been accurately ascertained. The 

 first plate in the intersecondary area rests between the first secondary 

 radials, this is followed by a single plate between the second secondary 

 radials, and above this the plates have not been determined. 



Arms and Pinnidw. — The number of arms is not known, because 

 we can not say that if two series have six arms, five will have fifteen. 

 Where onl}" two series are known, as in this case, and one has two 

 arms, and the other four, it is evident that the species has more than 

 ten arms, and less than twenty. From the appearance of the parts ex- 

 posed, on the right of the series first above described, I infer that there 

 are four arms in the adjoining series ; and from the parts exposed on 

 the left o'f the last described series, we have here the azygous area. 

 If this supposition is correct, then we have four arms in the right an- 

 terior series, two in the right posterior series, and four in the posterior 

 series. The free arms rise vertically. The} T are long and slender, round 

 on the outer side, and are composed of numerous cuneiform plates, 

 the length of four or more of which is only equal to the diameter of 



