54 



HCHINOIDEA. II. 



only one, the left, is distinct in the fragment preserved. By a very careful preparation it will certainly 

 be possible to make out fully the structure of the apical system in this very interesting form. 



As regards the pedicellarise Calymne agrees with the Pourtalesiaj in having rostrate pedi- 

 cellarise of the form common in that family. They are of two kinds (PL X. Figs. 5, 6), one with the 

 outer end of the blade rather widened and finely serrate, the other with the outer edge onlv little 

 widened and provided with few, rather large teeth. (This is, evidently, the form figured in the Chal- 

 lenger -Eehinoidea PI. XLIII. 24 and XLIV. 47 as a Clypeastroid-like pedicellaria.i The stalk maybe 

 rather thorny, as is well shown in the Chall. -Ech. PL XLIV. 48; probably it is the coarse-toothed 

 form which has the thorny stalk, the other form having it smooth ; but I cannot say this with cer- 

 tainty. The triphyllous pedicellariae are like those of Urech. naresianus. The miliarv spines (PL X. 

 Fig. 30) have the point widened so as to form a broad, fenestrated plate, finely serrate along the outer 

 edge; the shaft is very slender, consisting of fine rods, which are not connected with transverse beams, 

 except a few at the base. This form of spine also recalls those found in some Pourtalesise. ■ 

 Evidently Calymne is not very closely related to the Urechinida ; I think it must form a separate 

 group (family), as it cannot be transferred to the Pourtalcsiidir. the anterior ambulacrum not being 

 invaginated. (Comp. below p. 86.) 



The genus Phrissocystis is also referred to this family (by Meissner in Bronn. Classen u. Ord- 

 nungen , by Agassiz in the Preliminary Report on the Albatross -Echini, and by Doderleiu in 

 Eehinoidea d. deutschen Tief-See Exped.). This seems to be a rather unnatural place for this genus. 

 Unfortunately the structure of the plastron is not known, but so main other features point towards 

 Pala'opneiisfes that I think Agassiz is quite right in referring it to the new family Palcropucustida- 

 established by him (Panamic Deep-Sea Ech.), and I also think the establishment of that family 

 quite justified. 



20. Plexechinus hirsutus Mrtsn. 



PI. VI. Figs. S — 9, 12 — 16. PI. VII. Figs. 9, 19-20. PI. X. Figs. 2, 15 — 17, 19, 21. 23, 25, 27, 31—32, 34, 36 — 38. 



Th. Mortensen: Some new species of Eehinoidea. Vid. Medd. Naturh. Forening. Kobenhavn. 

 1905. p. 242. 



The outline of the test is almost regularly oval, especially in the smaller specimens; in larger 

 specimens it is straight across the anterior ambulacrum or even slightly reenteringly curved. On the 

 actinal side the anterior ambulacrum is a little sunken; the posterior interambulacrum forms a very 

 prominent keel, prolonged into a broad, little projecting anal snout, surrounded by a fasciole. The 

 abactinal side is beautifully rounded, except the posterior end, the odd interambulacrum not sloping 

 at all but forming a rather prominent hood over the periproct. This feature together with the keel 

 on the actinal side makes the posterior end much higher than the anterior. The anal snout is dis- 

 tinctly less prominent than in /'. cincf/ts, being scarcely discernible in dorsal view, a very conspicuous 

 difference from the latter species, as will be seen on comparing the figures 13, 14. PL VI with PL 58. 

 Figs. 2 — 3 of the Panamic Deep-Sea Echini , and the figures 12, 15 of the same plate with PL 55. 

 4 — 5 of the work quoted. — The whole of the test (except the ambulacra of the bivium on the actinal 



