PALAEOPNEUSTES. 143 



145, fig. 28) have rounded leaf-shaped valves (PI. 145, fig. 21) about .12-.15 

 mm. long. The tridentate are abundant, of two quite different types which 

 tend to intergrade, though true intermediates are rare. The stout tridentate 

 (or rostrate?) (PI. 145, fig. 22) have the valves .40-1.50 mm. long, but little 

 curved and rather abruptly expanded at the tip (PI. 145, fig. 26) below which 

 the margins tend to be involute and carry a few large teeth. The slender tri- 

 dentate (PI. 145, fig. 24) have the valves .50-2.10 mm. long, with the tips (PI. 

 145, fig. 25) pointed and involute. The calcareous particles in the tube-feet 

 (PI. 145, fig. 20) are widely scattered and not at all distinctive. 



Archaeopneustes niasicus. 



Palaeopneustes niasicus Doderlein, 1900. Chun's Auf Tief. Welt., figs., p. 360. 

 Archaeopneustes niasicus Koehler, 1914. Ech. Indian Mus. Spat., p. 54. 



This species was taken by the Valdivia off the west coast of Sumatra 

 in 261 fms. It is rather remarkable that it should resemble hystrix so closely, 

 but the pedicellariae are noticeably different, as ophicephalous occur and the 

 broad tridentate are very clearly rostrate in form. 



Archaeopneustes hemingi. 



Palaeopneustes hemingi Alcock, 1902. A Naturalist in Indian Seas, fig. 22, opp. p. 168. 

 Archaeopneustes hemingi Koehler, 1914. Ech. Indian Mus. Spat., p. 52. 



This is the Indian Ocean species taken by the Investigator in 224-284 

 fms. Many specimens were taken but only at a single station. The rostrate 

 pedicellariae as figured by Koehler are very characteristic. 



Palaeopneustes. 



A. Agassiz, 1873. Bull. M. C. Z., 3, p. 188. 

 Type, Palaeopneustes cristalxis A. Agassiz, 1873. hoc. cit. 



Like the preceding this genus consists of one West Indian and two Oriental 

 species, but the specific differences are very much better marked. Koehler in- 

 deed places (1914. Ech. Indian Mus. Spat. p. 62) spectabilis in Linopneusres 

 but while there is room for difference of opinion, in my judgment its nearest 

 relative is Palaeopneustes cristatvs. The latter shows in some specimens more 



