154 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Palaeotropus thomsoni. 



A. Agassiz, 1880. Bull. M. C. Z., 8, p. 80. 



Plates 145, figs. 44~46; 158, figs. 6, 7. 



This highly interesting spatangoid was taken by the Blake east of Charles- 

 ton, S. C, in 233 fms. Mr. Agassiz published no figures and gives only a very 

 brief description although he recognized the unusual nature of the specimen. 

 The two figures of the test, one (PI. 158, fig. 6) as seen from above, the other 

 (fig. 7) as seen from the side, bring out well its peculiar features. The oral 

 surface is so badly damaged no information can be given about the labrum and 

 its adjoining plates. The posterior ambulacra as well as the anterior continue 

 to the oculars in double series, though they become very narrow and the plates 

 alternate more or less. There are distinct pieces of a very narrow peripetalous 

 fasciole but it is strikingly incomplete. There are four nearly equal genital 

 pores, though the posterior are a little the larger. 



Of pedicellariae, there appear to be four kinds but no globiferous were 

 found. Of the ophicephalous, only one was found and that was very small 

 with valves only .12 mm. long plus the loop of .06 mm. Triphyllous pedicel- 

 lariae are also rare and very small; the valves are .07 mm. long and broader 

 than in josephinae. The tridentate are common but small; the valves (PI. 145, 

 fig. 46) are straight and more or less compressed, but only .15-25 mm. long. 

 The rostrate pedicellariae are quite distinctive; the valves are quite deep, 

 .25-.50 mm. long, and have the margin of the terminal opening (PI. 145, fig. 44) 

 with numerous teeth; the stalks (PI. 145, fig. 45) are very remarkable because 

 of the pronounced "limb" which is near the base, instead of below the tip. 



Pycnolampas. 



A. Agassiz and Clark, 1907. Hull. M. C. Z., 60, p. 252. 

 Type, Pycnolampas oviformis A. Agassiz and Clark, 1907. Op. cit., p. 2 



This genus was established for some small spatangoids from the Hawaiian 

 Islands allied to Homolampas. The specimens are obviously immature, as 

 even the largest has no genital pores, but the difference from Homolampas of 

 somewhat larger size is so evident that it is highly improbable that these indi- 

 viduals are the young of any species of that genus. The two most important 

 differences are the evidently petaloid nature of the posterior ambulacra, which 



