PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 803 



Pentamelrocrinus semperi A. H. CLARK, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 135 (listed); 

 Proc. U.S. Nat. Mus., vol. 34, 1908, p. 277 (listed); vol. 35, 1908, p. 117 (arm structure); Mem. 

 Australian Mus., vol. 4, 1911, p. 796 (Challenger locality off Port Jackson) ; Crinoids of the Indian 

 Ocean, 1912, p. 33 (identity), p. 251 (synonymy; locality); Smithsonian Misc. Coll., vol. 61, No. 

 15, 1913, p. 67 (published references to specimens in the B.M.; Challenger sta. 169; plating on the 

 disk described). GISLEN, Zool. Bidrag. Uppsala, vol. 9, 1924, p. 26 (pinnulation) ; Ark. Zool., 

 vol. 19, No. 32, 1928, p. 12 (notes). FELL, New Zealand Science Congress, 1947, p. 209 (listed). 



Pentamelrocrinus semperei FELL, Tuatara, Wellington, New Zealand, vol. 3, No. 2, 1950, p. 81 (in 

 key), text-fig. 6 (calyx and arm bases). 



Diagnostic features. The lowest pinnule is on the epizygal of the first syzygial 

 pair; the relatively long cirri, about 30 mm. when the arms are probably about 80 nun. 

 long, have the first three segments short but the majority about four times as long as 

 broad and very little expanded at the joints, particularly in the outer half of the cirrus, 

 which is hardly curved; the centrodorsal is relatively small, with only about XV cirri 

 and an irregular dorsal pole; the proximal brachials have only inconspicuous articular 

 tubercles and are not markedly swollen at the joints. 



Description of the syntype from Challenger station 169 [by A.M.C.]. The centro- 

 dorsal is rounded conical; 2.7 mm. ha basal diameter and 1.8 mm. high. There are 

 XVI well-defined cirrus sockets irregularly placed around the sides, and the dorsal 

 pole is rough and rather pitted. 



Three basal segments of one cirrus remain attached. All are short, the third is 

 about as long as broad. 



There are some detached cirri which may belong either to this specimen or to 

 the syntype from station 164, since the tubes in which they are kept were not stoppered. 

 The largest of these was probably a peripheral cirrus. It has lost at least 4 segments 

 from the base and probably 2 or 3 from the tip but the 17 remaining segments are 

 29 mm. long. All are about four times as long as broad. A less robust cirrus with only 

 the tip lost has 21 segments and measures 28 mm. The third segment from the base 

 is slightly longer than broad, the fourth is two and a half times as long as broad, the 

 fifth is four times as long as broad. This proportion continues to the last remaining 

 segment. The first nine segments have slightly expanded joints but those following 

 have straight sides. After the first 15 mm. the cirrus tapers evenly. No terminal 

 portion remains. Carpenter gave the number of segments as 26 and the length 30 mm. 



The proximal brachials to the second syzygy have almost parallel proximal and 

 distal sides but further out the brachials become relatively longer and more triangular. 

 The articular tubercles are low and inconspicuous and the brachials are not much 

 expanded at the joints. The first syzygy is at brachials 4 + 5 and is 1.8 mm. wide. 

 The second syzygy is variable, on the 5 arms it is twice at brachials 9 + 10, twice at 

 10 + 11, and once at 8 + 9. The length from the proximal edge of the first brachial to 

 the second syzygy at 9 + 10 is 10.0 mm. The longest remaining arm is 50 mm. When 

 complete it may have been double this as the tapering is slight. The intersyzj'gial 

 interval is 2 to 6 brachials. 



The first pinnule arises on the right side of the fifth brachial in 3 out of 5 cases. 

 The longest remaining one has 15+ segments, probably about 18, and is 7 mm. long. 

 The first three segments are short, the fourth and fifth are half again as long as broad 

 and the rest are up to two and a quarter times as long as broad. The pinnule on the 

 sixth brachial has 17 segments similar in proportions to those of the first one. The 

 segments are only a little expanded at the joints. 



