REPORT ON THE MONAXONIDA. 237 



throughout, but soft and spongy, with easily separable, parchment-like cortex. Surface 

 smooth between the conical processes, but rather harsh to the touch. Oscula on the 

 tops of conical processes. Pores (probably as in Latrunculia apicalis). 



Skeleton. — There is a dense dermal crust, composed as usual of a single layer of 

 vertically placed discasters ; and below this there is a loose, irregular reticulation of stylotts 

 •spicules, in which one may distinguish poorly developed lines of fibre, some running 

 towards the surface representing the primary skeleton lines. 



Spicules.— {a) Megasclera ; smooth styli (PI. XLV. fig 10), straight or very slightly 

 crooked, with evenly rounded bases and more or less hastately pointed apices, not very 

 sharp; size about 0"6 by 0'12G mm. (6) Microsclera, discastra; for these we refer to 

 PI. XLV. fig. 10a, and also to the description of the corresponding spicules in Latrunculia 

 aincalis, merely stating that they differ chiefly from the latter in having no apical pro- 

 longations ; the upper whorls are approximated so as to form a thick brush at the top, the 

 Uu-gest occupying the same position as in Latrunculia apicalis; length about 0"05 mm., 

 diameter of largest whorl about 0'044 mm. 



The form of the " chess-man " spicule is, as usual in the genus Latrunculia, the 

 most characteristic feature of the species. (This remark would scarcely be applicable to 

 Latruncidia cratera, Bocage,^ should the very minute size of the megasclera, viz., 0"I8 

 mm. long, as ascertained by calculation from the figure, which would at once distinguish 

 it from all the Challenger species, be confirmed.) ^ 



A slight variety, of which there is one specimen, from the same station as the types of 

 the species, has the " chess-man " spicule a trifle (but very slightly) elongated and the 

 whorls much further apart from one another as compared with the type ; thereby making 

 an approach to the Kerguelen species, Latrunculia hocagei, nobis. 



It would be curious, if it should prove to be correct, that there should be only one 

 form of mammiform processes in this species, that all should be conical and osculuni- 

 bearing, with no raised pore-areas. AVe are, however, strongly inclined to think, both 

 from the analogy of other species and from the enormous number of the projections, which 

 can scarcely all be cloacal tubes, that the raised pore-areas would be found to exist in 

 more perfectly preserved specimens, although in the Challenger specimens they are indis- 

 tinguishable from the osculum-bearing processes. 



Locality.— ^tsitww 320, February 14, 1876; lat. 37° 17' S., long. .-53° 52' W.; ofi' the 

 mouth of the Rio de la Plata ; depth, 600 fathoms ; bottom, green sand ; bottom 

 temperature, 3 7° "2. About ten specimens in poor condition, being a good deal 

 crushed. 



' Jorn. Acad, real Sci, Lisboa, vol. ii. p. 161, pi. xi. fig. 2. 

 2>See, however, the remarks after the next specie.s. 



