18 TH. MORTENSEN, ECHINOIDEA. 



different from that figured by Clark, as seen by a comparison of the figures. Ophi- 

 cephalous pedicellariae were not found. 



The spines are of the structure described and figured by De Meijere, except 

 that the miliary spines of the aboral side are somewhat more closely and finely 

 serrate at the point. 



13. Fibularia volva Agassiz & Desor. 



Pl. V, Figs. 12, 13, 16, 20, 27, 28. 



Fibularia volva. Agassiz 1873. Revision of Echini, p. 509. 



» » » De Meijere 1904. »Siboga» Echinoidea, p. 113. 



» II. L. Clark. 1914. Hawaiian a. o. Pacific Echini, Clypeastridae etc, p. 58. 



A single beautifully preserved specimen from 45 miles W.S.W. of Cape Jaubert, 

 24 m. (2/VII. 1911) may be referred provisionally to this species. At the present 

 stage of our knowledge of these small Echinoids it is impossible to form a definite 

 idea of the specific limits of the different species recognized, most of them being 

 known only from imperfect descriptions of naked tests. 



The specimen in hand measures 9 mm in length, 4,5 mm in height and 6 mm 

 in width. Through the dense, uniform coating of spines are seen 20 distinct meridian 

 lines of yellowish tubefeet, running from apex to mouth, viz. two in each ambula- 

 crum and two in each interradius. In the petaloid part of the ambulacra there is 

 one simple tubefoot adjoining each branchial tubefoot, situated adorally to the inner 

 (adradial) pore of each pair; in the outer part ot the petals there are two such simple 

 tubefeet between the branchial feet, and outside the petals they increase in number 

 so as to form a little duster of some twenty tubefeet to each plate, thus continuing 

 until the peristome. The whole way down the feet of each plate remain distinct, 

 the whole together forming the meridian line above described. In the interambu- 

 lacra there is the same distribution of these tubefeet, except that there are, of course, 

 no branchial tubefeet in the upper part. These groups of tubefeet do not appear to 

 be situated in grooves of the test, as is the case in F. cribellum, according to De 

 Meijere (Siboga-Echinoidea, p. 112). The pores of the petals are rather large, 

 rounded; there are 6 — 7 pairs in the postero-lateral, 5 — 6 pairs in the antero-lateral petals 

 and 5 pairs in the anterior petal. The genital pores are somewhat smaller than the 

 petaloid pores. The madreporic plate has about 16 small pores, arranged round a 

 single central tubercle, the posterior part remaining imperforate. 



The peristome is covered with numerous small plates; the same is the case 

 with the periproct. In the present specimen the anal opening lies on the top of a 

 small cone, with a circle of rounded grains at the edge. Whether this anal cone is 

 a normal feature or just the stage assumed at the evacuation of the excrements 

 can, of course, not be ascertained from this single specimen. 



The primary spines are ca. 0,8 mm long, simply rounded at the point, and 

 with a few serrations in the outer part; those around the peristome are somewhat 



