164 HAWAIIAN AND OTHEE PACIFIC ECHINI. 



Echinosoma hispidum Mortens. 



Phormosoma hispidum A. Agassiz, 1898. Bull. M. C. Z. XXXII, p. 77. 1904. Panam. 



Deep-Sea Ech., Mem. M. C. Z., XXXI, Pis. XXX-XLIX. 

 Echinosoma hispidum Mortensen, 1907. " Ingolf " Ech., Pt. II, p. 24. 



Gulf of Panama, west to the Galapagos Islands and north to the Gulf of California ; 



995-1421 fathoms. 



Plates 62, fig. 3; 63, fig. 4; 67, figs. b-11. 



The pedicellariae of this species are numerous and variable, but we 

 have found only tridentate and triphyllous ones, no ophicephalous. Mor- 

 tensen (" Ingolf " Ech., II, p. 25) says he has found " a kind of ophi- 

 cephalous pedicellariae." Examination of several good specimens, with 

 hundreds of pedicellariae, has not enabled us to find this form, so we 

 conclude it must be quite exceptional. The triphyllous pedicellariae are 

 abundant and not peculiar, though the neck may be twice or three times 

 as long as the head (PI. 67, fig. 10), and the stalk three or four times as 

 long as the neck ; the valves are .40-.50 mm. long and the width at the 

 tip is rather more than half the length. 



The tridentate pedicellariae appear in at least four different forms, but 

 they integrade with each other to such an extent it is not easy to draw 

 lines between them. The largest ones (PI. 67, fig. 4) are tolerably com- 

 mon ; the valves (fig. 5) are 3-4.75 mm. long, slightly curved, widened at 

 tip, and meet only for the terminal quarter ; the edges of the blade are 

 slightly involute, while the centre is occupied by more or less of a cal- 

 careous mesh-work. The stalk of these pedicellariae is scarcely as long as 

 the head, and there is almost no neck. A more abundant form of tri- 

 dentate pedicellaria is decidedly smaller (PI. 67, fig. 6), has the stalk two 

 or three times as long as the head and there is a short neck ; the valves 

 (fig. 7) are straight, 1-1.75 mm. long, not widened at tip or involute at 

 sides, and meet for their whole length. In another form (PL 67, fig. 8), which 

 seems to be very rare, the valves are narrow, nearly straight, a trifle 

 widened at tip, and meet for about three-fourths of their length. They 

 are 1-1.25 mm. long. A fourth form (PI. 67, fig. 9), which is also rare, 

 is the smallest of all, but has a long, thick neck and a stalk three to five 

 times as long as the head ; the valves are only .35— .75 mm. long, straight, 

 somewhat expanded at tip, and meet for nearly their entire length. 



The sphceridia (PL 67, fig. 11) are slightly elongated and seem to be 



