82 THE VOYAGE OF H.M.S. CHALLENGER. 



pedicellarise oi Asthenosoma grubii (PI. XLII. fig. 9) are very similar to those of Astropyga 

 (Revis. Echini, pi. xxiv. fig. 40). Of the globular-headed short-stemmed pedicellarige, 

 however, some difler totally from those of that group ; they are remarkable for the great 

 width of the base and of the upper extremities of the valves (PI. XLII. fig. 8, Asthenosoma 

 grubii). An interior and an exterior view of the valve of a similar pedicellaria of 

 Phormosoma luculentunn is given on Plate XLIV. figs. 25, 26, while, on the contrary, the 

 general structure of the long-headed pedicellarise of Phormosoma (PI. XLIV. figs. 19, 20, 

 Phormosoma tenue) closely resembles that of the same kind of pedicellarige in Centro- 

 stephanus (Revis. Echini, pi. xxiv. fig. 37), which are remarkable for the large open 

 meshwork structure of the central part of the valve (PI. XLIV. fig. 19, Phormosoma 

 temie, and PI. XLIV. fig. 36, Asthenosoma grubii). These vary greatly in size on 

 difierent parts of the test. This open reticulation is indicated in some of the Echinidae, 

 but is quite apparent in Pseudoboletia (PL XLIV. fig. 39). 



The rods which support these pedicellarise are uniform in structure, they resemble the 

 rods of the pedicellariae of the Diadematidas ; they all have a slight constriction at the 

 head (PL XLIV. figs. 24, 28, 31, 32). 



The EchinothuridsB also have (PL XLIV. fig. 34) short-stemmed globular pediceUariai, 

 resembling closely the abactinal pedicellariae of Aspidodiadema, but with coarser toothed 

 valvular edges. In addition to the remarkable long-pronged pedicellaria, figured by 

 Thomson as characteristic of the group, we have also remarkable bottle-shaped didactyle 

 pedicellarige, which are perhaps only modifications of the former (PL XLIV. figs. 21, 22, 

 Phormosoma tenue). They are at once distinguished by their regular reticulation, the 

 smaU size of the base, the broad fan-like expansion of the extremity, with the raised edges, 

 forming a deep triangular space at the upper end of the valve. This bottle-shaped pedi- 

 cellaria is only a modification of the ordinary type of pediceUarise in which the terminal 

 edge becomes raised to form a spoon-shaped valve. Another modification of it is formed 

 by the gigantic pedicellariae (PL XLIV. fig. 29, 29'), in which this cup-like cavity ex- 

 tends along the shank connecting it with the base (see also PL XLIII. fig. 1). 



Asthenosoma. 

 Asthenosoma, Gnilje, 1867, Jahresb. der Schles. Ges. f. Vat. Cult. 



*Asthenosoma grubii (Pis. XV., XVI., XVII., XXXVIII. figs. 1, 2, 4 ; PL XLII. 

 figs. 8, 9 ; PL XLIII. fig. 2 ; PL XLIV. figs. 32-36). 



Asthenosoma Gnihei, A. Agassiz, 1879, Proc. Am. Acad., vol. xiv. p. 200. 



This is a pentagonal species with rounded corners (PL XV. fig. 1, PL XVI. fig. 1), 

 quite flattened when in alcohol (PL XV. fig. 2), with nearly vertical ambitus. Thickly 

 covered on the actinal side (PL XVI. fig. 1) with curved, hollow, primary radioles, which 



