IIG Mr. II. J. Carter on the Oenus RosscUa. 



the body and their lieads respectively (fig. 4, b h) ; shaft smooth, 

 or only niicrotiibcrculate over the imbedded end ; arms more 

 or less flexuous, fine-pointed, ])artin<i; from the head of the 

 shaft at ditferent angles, covered almost thronghont with 

 minute spines, closely apjiroximated, amongst which, here and 

 there, is a much larger si)ine, curved and inclined outwards or 

 from the head of the shaft; average largest size 2 to 3-l2ths 

 by 5-18()0ths of an inch in the greatest diameters, both for 

 the arms and shaft respectively, the former for the most part 

 longer than the latter. B. Structural spicules (that is, of the 

 body or wall) of three forms, viz. : — 4. Nail-like or cmcially 

 headed, much like that last described, but with the shaft shorter 

 and the arms longer ; the former vertically placed in the wall 

 and the latter spread out horizontally over its external surface, 

 so as to support the lattice-like layer of minute sexradiatc 

 spicules imbedded in the dermal sarcode immediately above 

 and the shafts of the veil-spicules beyond ; arms more or less 

 cur\-ed inwards, so as to render the head of the spicule pro- 

 minent or monticular, thus characterizing the surface by a 

 number of conical eminences linked together by radiating 

 arms. 5. A long linear spicule, nearly straight, fusiform, often 

 presenting in the middle two or four tubercles corresponding 

 to the ends of the crucial branches of the sexradiatc central 

 canal, terminating in spined and more or less inflated ex- 

 tremities, but otherwise smooth ; average largest size 3-12ths 

 by 2-1800ths of an inch in its greatest diameters ; situated on 

 the inner side of the wall chiefly, where it forms, together 

 with minute sexradiatcs and flesh-spicules, the surface of the 

 concavity. 6. Sexradiatcs, of different sizes, with arms of 

 equal length, spined and pointed, chiefly composing the lattice- 

 like structure, whicli, in the way above stated, covers the 

 whole of the dermal surface with quadrangular interstices 

 from l-300th to l-150th of an inch in diameter, c. Flesh- 

 spicules of four rosette-forms, chiefly situated in the surface- 

 layer of the cavity : — 7. Sexradiatc rosette with smooth 

 pointed arms of equal length ('Annals,' 1873, vol. xii. pi. xiii. 

 fig. 1). 8. Sexradiatc rosette with short arms and double 

 rays {ib. fig. 3). 9. Very minute sexradiatc rosette with 

 numerous straight capitate rays (PI. X. fig. 7, b). 10. Sex- 

 radiate rosette with thick, sparsely spined arms (fig. 6, a), 

 whose inflated ends support four or more indistinctly capitate 

 rays (fig. Q,b c): rays microspined, thick at first, then becoming 

 finely attenuated and terminating in a liardly perceptible capi- 

 tate inflation (fig. 6, d) ; rays at first straight and parallel like 

 the prongs of a dinner-fork, becoming more or less divergent 

 towards their extremities (fig. 6) ; average largest size of the 



