Hamhach — Revision of the Blastoideae. 7 



giving off five branches, one for each ambulacrum, and run- 

 ning through the center of the lancet piece. From the 

 foregoing we see that the whole center of this system as 

 well as the branches run through the midst of a calcareous 

 substance, and their lumen is so small 

 that they are frequently found to be 

 obliterated. It is therefore hardly 

 possible that these fine channels could 

 have served for anything else than the 

 reception of the nervous system, giv- 

 ing us an analogous arrangement to 

 what we find in our living Asteroidea ; 



see Fiff. 4. „ 



^ Fig, 4. 



The second part, ^. e., the lateral 



expansion in the typical species above mentioned, is not un- 

 like the Greek letter delta, from which the name originated, 

 or resembles an arrow head with a very acute surface up- 

 wards and an obtuse one downwards, having on each side a 

 spur, running obliquely down and inwards, so as to be ex- 

 ternally concealed by the upper points of the fork pieces. 

 The upper acute surface differs very much in the different 

 species and often in one and the same species, being subject 

 to great variations, so that we find it often very acute and 

 bent inwardly, or very broad and bent outwardly. 



In other species, where the calyx consists of only a very 

 thin shell, as for example in C. melo, the laminar blade widens 

 immediately so that the whole piece is placed more horizon- 

 tally on the summit of the calyx, and hardly any division 

 between base portion and lateral expansion takes place, ex- 

 cept the incision for the construction of the genital openings, 

 and this same condition can be observed throughout the 

 whole juvenile state of the body. In other species again, as for 

 instance in C sayi, the lateral expansion nssumes such an 

 enormous size that it occupies almost three fourths or four 

 fifths of the entire calyx, and in others, as in G, norwoodi, 

 the whole deltoid piece has a triangular form and the genital 

 opening pierces directly through the center of this piece, but 

 with only one external opening, bifurcating within the shell, 



