180 Prof. P. M. Duncan on the 



placed upon soft necks, and these are of different lengths, and 

 so are the stems on which the necks are situated. 



In SaJmocis the distribution of pedicellarioe is not the same 

 as in Temnoplenrus. 



Tlie peristoraial membrane of Sahnacts hicolor has \q.x\ 

 buccal plates, which not only carry tentacles but a crowd of 

 rather long'-stemmed ophiocephalous pedicellariaj or tryphylta 

 occurs, and with them are sometimes found small <i,lobifera 

 with unusually long valves; these may be on stalks or they 

 may have soft long necks besides stalks, and they are smaller 

 and not so tumid as the globifera of the test itself 



Upon the test there are many pedicellarife, and the globi- 

 fera are usually tumid at the base, but with a duck- mandible 

 shaped valvular end ; they are very regularly fenestrate, but 

 the median thickening and ridge observed in Temnophunis 

 are wanting. In both genera there are usually pedicellarire 

 close to the pits of the sutures. 



The pedicellariai with long and short soft necks are common 

 and are of all kinds. 



The Madreporite. 



The madreporite of the Teranopleurina3 is not like that of 

 Echinus and Cidaris, for instead of the upper surface being 

 spongy-looking and with very irregular openings, it is well 

 defined in Temnojyleurus^ Sahnacis^ Amhlypneustes, &c., and 

 the water-openings are separate and large, and when decalcified 

 ihey are tubular, andresemble distant cylindrical straight pipes; 

 they have thick edges or sides lined with epithelium. The 

 height of these cylindrical pipes is not great. The madre- 

 porite is well separated from the structure of the basal plate in 

 wdiich it is placed. 



Valentin described and drew some fusiform, band-like 

 muscular slips which arise at the inner edge of the peri- 

 procteal ring and pass inwards to the edge of the anus. He 

 called them " motores ani."" They are well seen in Tem- 

 nopleurus^ and staining with carmine shows very thin fibrillar 

 muscular slips, with a considerable quantity of nerve filaments. 

 The slips are distinct and separated. 



EXPLANATION OF PLATE XI. 



Fig. \. Microcyplms zigzag, Agass. Side view of the plates on one side 

 of the median ambiilacral suture 5 knobs and sockets; dark 

 lines indicating the sutures of the component plates of the 

 geometrical ambulacral plates. X refers to fig. 9. ]Mag. Pp. 

 Ill, 11:3, IIG. 



