480 DR. P. H. CARPENTER ON THE CIRRI OF CERTAIN COMATULuE. 



Seine bank at 88 fathoms ; while the depth on the Tunis coast where the ' Porcupine ' 

 dredged varied from 50 to 120 fathoms, and Marion found the species to be'most abundant 

 at Marseilles in 100-200 metres. Temperature variations again seem to have nothing 

 to do in causing this difference, for there arc plenty of long-jointed cirri in the 

 individuals brought up from 220 fathoms at a temperature of 52° Fahr., which is very- 

 near that observed in the Minch, while the Mediterranean water on the Tunis coast 

 was much warmer. 



These variations in the form of the cirri are the more remarkable because in most 

 Crinoids these organs are very constant in their characters. In fact, among the 

 Pentacrinkbe there are several species of which the cirri are so similar that they can 

 hardly be differentiated when removed from the stem. In the genus Actinometra the 

 the cirri are, as a rule, lew in number ami poorly developed ; but the lower pinnules of 

 the arms often reach a considerable size and are provided with keels and processes of 

 different kinds ; and in some species, such as Actinometra Solaris and its allies, indi- 

 viduals from different localities present much the same sort of variation in the pinnule- 

 characters as we have seen to occur in the cirri of Antedon phalangium. 



DESCRIPTION OF PLATE LVII. 



[All the figures are x 5, except figs. 13, 20, 22, which are X 10.] 



Type A. Long-jointed. 



Figs. 1-6. Young cirri of the large rudimental type ; from the Seine bank. 

 Figs. 8, 9. Similar forms from the Tunis coast. 

 Fig. 7. Adult cirrus from the same locality. 



Type B. Intermediate. 



Figs. 10, 11, 13, 18. From the Seine bank. Fig. 13 represents a very young cirrus, probably 



of the small mature type. 

 Figs. 12, 17, 19. From the Tunis coast. 

 Figs. 14, 15. From oft' Cape Sagres. 

 Fig. 16. From the Mincb. 



Type C. Square-jointed. 



Figs. 20, 22. Young cirri of tbe small mature type ; from the Seine bank. 

 Figs. 23-27. Older cirri from the same locality. 

 Figs. 21, 28, 29. Older cirri from the Minch. 



Type D. Short jointed. 



Figs. 30-32. Immature cirri of the large rudimental type; from the Minch. 

 Fig. 33. Adult cirrus from the same locality. 



