BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 13. AFD. IT. N:0 5. 59 



the Clypeastridse, the ambitus is: ovatus, ovalis, orbiculatus, 

 sub-orbiculatus. 



The > Centrum) of the dorsal surface, »cum area pentagona 

 angulis perforatis», »apicibxis puucto perforatis>, ex puiictis 4, 

 2, perforatis», is the calyciBal system with its oostals and their 

 sexual apertures. The words, of Ch-peaster rosaceiis: »ex 

 puuctis perforatis minimis in orbem positis , appear to refer 

 to the madreporite. In most of the specimens of the Museum 

 noAv remaining these parts are missing, from having been de- 

 stroyed by the cooking process. 



The »Basist is the under side, with the »apertura», the 

 peristome in the »Regulares, or 



the »centrum», ; foramen centralo in the >Irregulares>, 

 the centrum reniforme» in the Spatangi. 



The »Pori>. are the pedicellar pores. In the Regulares 

 he regards them as single and counts them singly, not as 

 geminous and by pairs, lie remarks on their arraugement in 

 »seriesv and in »ordines obliquos». In the Irregulares he ob- 

 serves their structure in the petala, naming them there ^pun- 

 cta perforatai, and makes use of the same expression in his 

 special observations on the Echimis Diadema. 



The > Ambulacra» properly answer to what is now called 

 zonae porifera;, the fascife of Lamarck and Blainville. In 

 the Regulares LiNNyEUS counts ten ambulacra, which in his 

 fifth species approximate, so as to form five pairs, in the sixth 

 the like, and in the seventh, Echinus Diadema, and the eighth, 

 Echinus Cidaris, become almost contiguous, two and two, so 

 closely as to appear as forming only five ambulacra. In the 

 three last among the Regulares, whicl^ are Echinometr.T, there 

 are again ten separate ambulacra. 



In all the Irregrnlares L1NN.EU8 counts but five ambulacra. 



The Radii are the petala in all the Irregvilares. In the 

 Regulares the same term, in the special remarks on the Echinus 

 Diadema, exceptionally refers to the peculiar conforraation of 

 the upper part of the »tive ambulacra. 



The »Aee^e 1. Areol^ minores^, >,angustior€sy>, »intennedio'» 

 are the spaces included between two zonae porifera^ or »ambu- 

 lacra» L. This space, taken together with the two zonöe, con- 

 stitutes the ambulacrum of the present terminology, introduced 

 by Lamarck*} and Bl aix ville-). 



') An. 3. Vert. III, p. 4, 40. 



-) Diet. se. nat, XXXVII, p. 62. 



