MONOGEAPH OF THE EXISTING CRINOIDS. 



75 



Chiasma. — The figure formed by the division of the dorsal nerve trunks within the 

 axillaries (fig. 62, p. 89). 



Immediately upon entering the axillary the nerve cord divides into two parts 

 which run each to the center of one of the two distal articular faces. A trans- 

 verse connective unites these two branches just before they emerge from the 

 distal faces of the axillary. Shortly after the branchmg of the primary nerve 

 cord a small branch is given off from the inner side of each derivative; these 

 two branches run obliquely outward, distally crossing each other and immedi- 

 ately merging with the transverse connective. 



Fig. 36. 



Fig. 37 



Fig. 38. 



Fig. 39. 



Fig. 40. 



Figs 36-40-36 A typical cryptostoarthrt from a specimen of Comatwla pectinata feom Sinqapoee. 37, The pseddo- 

 stzygy betVeex the ossicles of the IBe series in a specimen of Comasteb frcticosus from the Philipplne Islands. 

 IS The two articulating surfaces of the perfected pseddosyzygy between the first two brachuls ln the type 

 specimen of Comatula purpurea from .Vustralu. 39. The perfected pseudosyztgy between the 0S..ICLES of the 



IBR SERIES IN A SPECIMEN OF CoMATULA MICRASTEE FROM THE ANDAMAN ISLANDS. 40, TlIE PERFECTED PSEODOSYZYGY 

 between the OSSICLES OF THE OUTER DIVISION SERmS IN A SPECIMEN OF COMASTER FRUTICOSUS FROM THE PHILIPPINE 



Islands. 



The chiasma within the axillaries is a reduplication of conditions accom- 

 panying the division of the primary nerve cords within the calyx (see figs. 62-64, 

 p. 89, and pp. 350-354). 



Cirrdl.—K smglo cirrus segment (see figs. 1, p. 60, and 4, p. 63). 



arrival. — Same as Cirral. 



Cirrhi. — See Cirri. .... 



Cirri.— In the comatuUds and pentacrmites; jomted appendages ansmg in the 

 former from the centrodorsal, and in the latter from specialized coluiunals 

 (nodals) wliich occur at regular intervals lliroughout the st<>m (see figs. 1, p. 

 60, 4, p. 63, and 127, p. 197 and pp. 258-312); (see Radicular cirri) . 



