General Notes 49 



IDENTIFICATION OF A SUPPOSEDLY ANOMALOUS 

 ECHINODERM.* 



In 1902 Dr. Hubert Lyman Clark described, under the title of "An 

 Extraordinary Animal," f a very curious creature, evidently an echi- 

 noderm, which he was unable to place satisfactorily. He says that "it 

 probably is an echinoderm, but whether an echinoid or a holothurian I 

 am unable to decide * * * xhe whole external appearance of the 

 lower part of the animal is * * * quite similar to the body of the 

 holothurians, Sphxrothuria or Echinocucumis. But the spines when 

 examined under the microscope appear more like echinoid spines * * * 

 There can be little doubt that the specimen is a monstrosity, but of what? 

 My own opinion is that it is a holothurian, related to Sphserothuria, but 

 the spines and the 'digestive tube' (?) are very much like those of an 

 echinoid. — The most puzzling question to me is, how did an animal with 

 apparently no mouth or aims and no means of locomotion reach such a 

 considerable size ?" 



The specimen is preserved in the U. S. National Museum (Cat. No. 

 19,899) and, as it seemed to me desirable to identify it positively if 

 possible, I recently undertook an independent study of it. 



As Doctor Clark's description is not quite accurate in certain details, I 

 offer the following supplementary notes. 



General Form. — The specimen is composed of two quite distinct 

 portions, a larger, ovoid in outline with the greater diameter 13 mm. and 

 the lesser 11.5 mm., in end view circular, 11.5 mm. in diameter; and a 

 smaller, broken away on one side, consisting of a very irregular half 

 cylinder with the ends more or less in-curved, measuring 12 mm. in 

 length and 5.5 mm. in width, which is attached to one side of the larger 

 part in the direction of the longer axiis, nearer the smaller than the 

 larger end. The border of the larger part opposite the attachment of the 

 smaller is slightly flattened. 



Covering of the Larger Part.— The larger portion is entirely enclosed in 

 irregular polygonal plates of various sizes, each of which bears from one 

 to six (usually from one to three) jointed spines, and a few in addition a 

 pedicellaria, which superficially resembles a short, small rounded-conical 

 spine. The spines, most of which are broken, appear to be cylindrical, 

 with a more or less abrupt conical tip. W^ithin the area delimited by the 

 smaller part and the missing portion the investment consists of a smooth 

 pavement of very irregular polygonal plates which are somewhat smaller 

 than those of the free wall. 



Covering of the Smaller Part. — The smaller portion is composed, insofar 

 as it is preserved, of six columns of narrow elongate plates which carry 

 long spines, longer than the spines on the surface of the larger part, in a 

 single median row, but no pedicellarise. The six columns are webbed by 

 perisome, which may carry a few additional plates. Extending laterally 

 from the first and sixth of these columns are two horizontal rows of 



• Published with the permission of the Secretary of the Smithsonian Institution. 

 t Zool. Anzeiger, vol. 25, 1902, pp. 509-511. fig. p. 510. 



