100 PANAMIC DEEP SEA ECHINI. 



Loven ^ has described the changes taking place in the actinal plates of 

 the ambulacra of Asthenosoma varium as they flow Cidaris-like onto the 

 actinal system. It is probable that the absence of interradial buccal plates 

 in the Echinothuriae is due to the persistence of the primordial inter- 

 ambulacral plate; in Cidarid£e the primordial pair is resorbed^ and the 

 interambulacral zone comes imder the same conditions as in the Echinidae^ 

 where there is a constant flow of the coronal plates onto the actinal system 

 more rapid in the ambulacral zone than in the interambulacral area, though 

 it may often be difficult, if not impossible, to detect the formation of the 

 minute actinal plates as coming from the disintegration of either the am- 

 bulacral or interambulacral areas.^ 



On Plate 33, fig. 3 is given an abactinal view of the pyramid of a 

 Phormosoma hispidum 120 mm. in diameter, and on PI. 46, fig. 1 that of 

 a large specimen, 203 mm. in diameter, seen from the same point of view, 

 with a slightly oblique view of the same (PI. 46, fig. 3) showing the position 

 of the compass with reference to the auricles. The dental system of 

 Asthenosoma has been figured and described by Loven.* That of Phor- 

 mosoma differs in some essential points from that of Asthenosoma. Seen 

 in profile the pyramid of the former is more slender and drawn out at 

 •the actinal extremity (PI. 47, figs. 1, 3). See Thomson, loc. cit. p. 735, 

 PI. LXIII. 



Station 3362, east of Cocos Isd., 1175 fathoms. Lat. 5' 56' N. ; Long. 

 85° 10' 30" W. Bott. temp. 36°.8. Gn. M. S. rocky. 



Station 3375, south of Malpelo Isd., 1201 fathoms. Lat. 2° 34' N. ; Long. 

 82° 29' W. Bott. temp. 36^6. Gy. glob. ooze. 



Station 3376, south of Malpelo Isd., 1132 fathoms. Lat. 3^ 9' N.; Long. 

 82° 8' W. Bott. temp, 36^3. Gy. glob. ooze. 



Station 3392, southwest of Cape Mala, 1270 fathoms. Lat. 7' 5' 30" N. ; 

 Long. 79° 40' W. Bott. temp. 36°.4 Hard. 



Station 3400, about 30 miles east of Chatham Isd., Galapagos, 1322 

 fathoms. Lat. 36' S.; Long. 86° 46' W. Bott. temp. 36. Lt. gry. glob. ooze. 



Station 3413, north of Culpepper Isd. Galapagos, 1360 fathoms. Lat. 

 2° 34' N.; Long. 92° 6' W. Bott. temp. 36^ Glob, ooze dk. sp. 



Station 3431, off Altata, Gulf of Califa., 995 fathoms. Lat. 23' 59' 

 N. ; Long. 108° 40' W. Bott. temp. 37\ Lt. br. m. glob. 



' Lovdn, Echinologica, p. 2(5. 



^ Doederlein. .lapanische Seeigel, p. 32, PI. IX. fig. 6. 



' Loven, Ecliiiiologica. pp. ;U-34. PI. XII. 



* Kchinologica, pp. 52, 53, Fig. 4. 



