200 PANAMIC DEEP SEA ECHINI. 



The madreporic body has developed between the two posterior genital open- 

 ings. The stone canal is prominent when seen from the interior of the test 

 (PI. 108, fig. 9), and there are also traces of the suture between two of the 

 genitals visible from that side. 



In Agassizia the change of position of the fasciole with age is very 

 marked ; though it is on the same plates in the anterior part of the test, yet 

 it is almost on the ambitus when seen from the actinal side (PI. 108, figs. 

 1, 6). At the anal extremity the fasciole is close to the anus in a specimen 

 of 5 mm. (PI. 108, fig. 4-), while in a specimen of 16 mm. it forms a sharp 

 angle and crosses the odd posterior interambulacrum on the second plates 

 from the sternum (PI. 108, figs. 6, 8). 



There are several genera in which the anterior poriferous zone of the 

 petaloid anterior ambulacra is modified or partly atrophied. Among the 

 tertiary types Lambertia^ and Atelospatangus,^ related to Maretia and 

 Hemipatagus, have, as in the recent Agassizia, and Nacospatangus, a rudi- 

 mentary or totally absent anterior zone. In Agassizia and Nacospatangus 

 the lateral ambulacra are barely petaloid, while in the tertiary genera they 

 are petaloid. Oppenheim ^ has called attention to the existence of this 

 whole or partial atrophism in Hemipatagus and Parabrissus.^ In Maretia 

 and Lovenia the distal pores are part of the petals, they disappear or are 

 rudimentary at the abactinal pole. In* Nacospatangus the distal pores disap- 

 pear ; in Agassizia the anterior zone only of the anterior lateral ambulacra 

 is absent. 



Spatagodesma DiomedsB A. Ag. 



Spatagodesma Diomedee A Ag., Bull. M. C. Z. 1898, XXXII, Xo. 5, p. S3, PI. XII. fig. 8. 



Plates lOG ; 107. 

 The general aspect of Spatagodesma shows that it is an embryonic stage, 

 yet the development of the fimbriated tentacles of the phyllodes (PI. 107, 

 fig. 7) of the double pores on the plates of the anterior ambulacral system 

 (Pis. 106, fig. i; 107, fig. 4) would seem to indicate, judging by analogy 

 with Agassizia, that it possessed the principal characters of the adult. 



1 Lambertia, Paln-ontog. 47, Tl. 10, fig. ^ 1900, p. 112. 



^ Koch, A., Die Alttertiiiren iichiniden Siebenbiirgens. Jahrb. d. K. Geol. Anstalt, VII, 1885, 

 I'l. VII, fig. 4, p. 115. 



8 OppoDheim, P., Protok. d. Marz Sitzung. Zcit-?. d. deutsch. Gwl. Ges. 1809. 51, p. 28. 



* Parabrissus is a Brissoid having only tlie posk^rior zone of the anterior lateral ambulacra devel- 

 oped. See Bittuer, A., Verhandl. d. K. K. Geol. Reichsanstalt, 1891, p. 133, fig. p. 135. 



