144 DISCOVERY REPORTS 



big plates along the entire lengths of the pinnules and many spicules in the tentacles ; 

 and that those living intermediately are intermediate in character. But Mortensen 

 (1918, p. 19) found no plates, not only in four specimens from South Georgia, but in 

 sixteen from the east side of Graham Land. On the other hand, Grieg (1929a) described 

 the pinnules of seven specimens from the Bransfield Strait as having well-developed 

 cover-plates. 



The pinnules of thirty-eight Ross Sea specimens, twenty from the present collection 

 and eighteen from the National Antarctic and British Antarctic Expeditions, were 

 examined. Thirteen have plates along the ambulacra and spicules in the tentacles ; in 

 eight the plates are strongly developed, in five they are small and scattered. Another 

 thirteen have small and scattered plates but no spicules. One specimen has spicules 

 in the tentacles and no plates along the pinnule ambulacra ; eleven have neither plates 

 nor spicules. Two pinnules of a small Challenger specimen from Kerguelen were ex- 

 amined. One has a single diminutive plate near the tip, the other none. 



That the presence of highly developed plates and many spicules is not a sign of 

 immaturity is shown by the following table (p. 145), in which forty-six specimens from 

 the Bransfield Strait and the West Graham Land region are arranged in order of age, so 

 far as that is shown by the number of segments comprising their longest cirri. 



The table shows that it is not generally the immature but the larger that have the 

 most highly developed plates. Specimens taken from one place may vary in the degree 

 of their plating: for example, the smaller of the three specimens from St. 175 has highly 

 developed plates and many spicules while the other two have none. 



Although Minckert (1905, p. 499, fig. 2) described P. vanhoffenianus as being dis- 

 tinguished from P. kerguelensis by, among other things, the possession of a skeleton 

 along the pinnule ambulacra, his drawing, to illustrate the plating, shows no plates but a 

 reticulation in the ambulacral lappets such as I have seen in a large number of specimens. 

 It is formed of pigment. Hartlaub (1912, p. 485) describes the same appearance. 

 I have not noted it as present in specimens from South Georgia, bvit as being of frequent 

 occurrence in those from the South Sandwich Islands, the Bransfield Strait, the region 

 west of Graham Land, and the Ross Sea. It may occur together with, or in the absence 

 of, plates ; if the former, in such a way as to suggest to me that it follows a reduction in 

 the size of the plates. 



Florometra mawsoni A. H. Clark (Plate III, fig. 2) 



Solanometra antarctica (part) Clark, 1913, p. 61. 



Promachocrimis {Promachocrimis) kerguelensis (part) Clark, 19150;, p. 130 (bottom of page), pi. iv, 



figs. I a, b. 

 Florometra mawsoni Clark, 1937, pp. 10-14. 



St. 180. II. iii. 27. Schollaert Channel, Palmer Archipelago. 160-330 m. Gear OTL. Bottom: 

 mud and stones. One specimen. 



St. 181. 12. iii. 27. Schollaert Channel, Palmer Archipelago. 64° 20' S, 63° 01' W. 160-335 m. 

 Gear OTL. Bottom: mud. Two specimens. 



