DESCRIPTION OF A SPECIMEN OF HOLOPUS RANGII D'Orb. 

 FROM BARBADOS. 



[During his last days at the Museum, Professor Agassiz was occupied in preparing a paper on 

 Holopus for the Zoological Results of the Hassler Expedition. The single specimen in his pos- 

 session was kindly loaned him for study and description by Governor Rawson of Barbados. 

 As there are no good figures of this remarkable Crinoid, the drawings thus far prepared for Pro- 

 fessor Agassiz are published, together with a short description by Mr. Pourtales of this most 



interesting genus. 



ALEXANDER. AGASSIZ. 

 Cambridge, February, 1874.] 



The specimen was attached by a broad, incrusting calcareous base, but 

 slightly more expanded than the body, which is thick, inversely conical, bent 

 towards one side, of a hard, semicalcareous substance, having under a magnifier 

 a very delicate shagreen-like appearance. There are no sutures discernible 

 with certainty, though in some parts there appear to be faint indications of 

 them. I did not feel justified in making attempts to render them more 

 apparent by preparation. There are two rows of blunt tubercles on the 

 body part, corresponding to the middle of each arm (PI. X. Figs. 2, 3, 7), a 

 small tuberculated area is also noticeable near the border of the calicle be- 

 tween these rows (Figs. 3, 4), and scattering tubercles are found over other 

 parts of the body. Ten arms originate in pairs from five axial joints ; the 

 original specimen of D'Orbigny is described as having had but eight, and was 

 certainly anomalous. The axial joints are pentagonal with rounded angles, 

 hemispherically swollen and tuberculated in the middle, closely joined to each 

 other laterally;* the tubercles on these joints are in three irregular rows, 

 one in the middle and one corresponding to the middle of each arm (Figs. 

 2, 3). The inside of these joints is deeply channelled in the middle. The 

 arms are composed of thick, short joints, wedge-shaped, swollen and tubercu- 

 lated ; the articulations form a deep transverse furrow. There are no syzy- 



* Figs. 3 and 6 show apparently a small plate at the lower corner of one of the axial pieces. It is only 

 an accidental fracture. 



