,. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:<> 2. 165 



KONGI 



Gissocrinus macrodactylus. 



(Plate IX, tigs. 316 325). 

 187S Angelin, leonographia, p. 1<>, Tab. XVIII, fig. 1. 



Diagnosis. 



Dorsal Gup conical, bighér than wide; its plätes with strong axial ridges. IBB higli. 

 BB higlier than wide. KR higher than wide; facet less than half width. IBr 3 or 4. 

 IIBr 3 or 4. Arms branch 4 (5?) times, and are slender. Arm-ossicles higher than wide, 

 with rounded backs and parallel sides, compressed laterally. Ventral Sac vertical; composed 

 of parallel series of quadrangular j)lates lying side by side; with imbricating transverse 

 folds. Stem-ossicles round or subpentagonal, low, alternating in height, with rounded edges. 



The type-specimen of this species, No. 115 Ang., is a complete crown with two 

 stem-fragments, 22 mm. and 28 mm. long, proved to belong to it by the fitting of the 

 matrix in which they lie. I also refer to this species, with slight doubt, an arm-fragment 

 (hg. 325), which I am assured is a type-specimen of Myelodactylus gracilis Ang. (see p. 

 40). Beside these no other specimens of the species are known. 



Descriptiou of the Type-specimen. 



Dorsal cup conical; ornamented with strong axial ribs as in G. g.oniodckctylus. 

 Height 11 mm.: width at base 3.75 mm.; width above 9 mm. (tigs. 316 — 318). 



IBB 3. The single one, which below is nearly as wide as the others, is in 1. j>ust. 

 radius. They rise up sharply from the stem, with long adjacent sides. Seen from with- 

 out 1. post. IB is pentagonal; its height is 3.4 mm., the length of its side 2.25 mm. 



BB 5, hexagonal, and post. B heptagonal; elongate. Height 5 mrn.; width below 

 3.25 mm.; width above 4 mm. 



Kli 5; the interradial portions bend in sharply about the level of the facet. Height 

 to bottom of facet 3 mm.; width below 4.25 mm.; width above 4.6 mm.; length of side 

 about 3.2 mm.; width of facet 2.2 mm. The axial canal is distinct. 



Arms about 45 mm. long, extend to VBr or possibly VIBr, and are of generally 

 slender appearance (tigs. 316, 319). The ossicles as seen from the back are higher than 

 wide, with parallel sides and no distal ridges. Their backs are smoothly rounded. The 

 axial canal is distinct in the proximal region. 



The ventral groove with its covering-plates appears to have been of much the same 

 nature as in preceding species of this genus (figs. 320, 321). 



Anal structures: .r hexagonal, supporting 3 plates. 



The median proximal plate of the Ventral Sac is of the same shape as x (lig. 318). 

 The ensuing plates, primitively hexagonal, soon become quadrangular and parallel. They 

 have very strong upturned transverse ridges, which give the sac an imbricated appearance 

 (hg. 322). 



The Stem is preserved to a length of 50 mm., and has a diameter of 3.6 mm. 

 The ossicles are round or obscurely pentagonal, with a quinquelobate axial canal of 1 mm. 



