118 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Conolampas, whereas in Echinolampas the primordial interambulacral plates 

 are all in the basicoronal row. 



Minor features of this interesting genus are the characteristic triphyllous 

 pedicellariae and a notable arrangement of spicules in the tube-feet. These 

 latter are perhaps only specific characters but as the genus is monotypic, they 

 may properly be described here. Pedicellariae are quite common and three 

 sorts occur but the ophicephalous are least frequent. The tridentate vary 

 greatly in size but not in form. The valves (PL 144, figs. 30, 31) range from 

 .08 to .72 mm. in length and are in contact only at or near the tip; in the larger 

 ones the margins of the valves tend to become sinuate but are never very 

 markedly so. The ophicephalous pedicellariae are much like those of Echino- 

 lampas sternopetala but are much larger; the valves (PL 144, figs. 26, 27) are 

 about .30 mm. long with the loop .07-. 13 mm. more. The triphyllous pedicel- 

 lariae are quite odd; the valves (PL 144, figs. 28, 29) are only .07 mm. long 

 but they are strongly curved and though convex on the back basally are 

 concave distally; there is a large lumen through the apophysis. 



The miliary spines are little or not at all swollen at the tip and are usually 

 a little prickly. Sphaeridia are common and measure about .20 mm. in length 

 (PL 144, fig. 25). The calcareous particles or perforated plates in the tube-feet 

 (PL 144, fig. 32) are rather numerous but are not crowded; they are arranged 

 in three longitudinal series, with their longer axis at right angles to the axis 

 of the foot and their shorter axis at right angles to the surface of the foot ; they 

 are thus piled up one on another vertically. 



URECHINIDAE Lambert. 



This family and the three following, comprising the group of meridosternous 

 spatangoids, has been so recently and so well discussed by Mortensen (1907. 

 Ingolf Ech., pt. 2, p. 39-89) that there is little to add to his results. The 

 material accessible in any or all of our museums is not sufficient to settle satis- 

 factorily all the debatable points, and that which is at hand for my work leaves 

 much to be desired. My work fully supports Mortensen's conclusions and I 

 therefore shall only add the data secured on material which was not available 

 to him. Whether the four families here recognized are really natural groups 

 is still open to suspicion but it is at least a convenient arrangement and cer- 

 tainly not unnatural. There is no question that the Urechinidae are more 

 primitive than the Pourtalesiidae but whether it is really the oldest group of 



