REPORT ON THE CALCAREA. 01 



Gastric quadriradiate spicules. — Basal ray centrifugally, apical ray centripetally directed, lateral 

 rays lying parallel to the inner surface ; all rays of the same average diameter (0-015 mm.), 

 lying in the same or almost in the same plane ; basal ray straight, tapering from the base 

 to a sharp point, forming witli each of lateral rays an angle varying from 9G° to 100°, average 

 length 0'25 mm.; lateral rays straight, occasionally slightly curved, either cylindrical or 

 tapering from the base to approximately sharp points, usual length 0'2 mm.; apical ray 

 straight, cylindrical, bluntly pointed, forming with basal ray an angle varying from 180' 

 to 1G5°, of the same length as the lateral rays, often rather shorter and thinner. 



Triradiate spicules of the parenchyma. — Sagittal; always of the same average diameter (0018 

 mm.), usually tapering from the base to sharp points, forming three angles of 120°; 

 basal ray straight, reaching 0"3 mm. in length, often shorter (0 - 2 mm.) ; lateral rays 

 curved forwards, their average length 0'2 mm.; many of them show a rudiment of the 

 fourth ray, occasionally reaching 01 mm. in length, which, like that of tlic gastric quadri- 

 radiate spicules, lies almost in the same plane as the facial rays, being, however, always 

 sharp-pointed. 



Derma/ triradiatf spicules. — Of the size and form of the triradiate spicules of the parenchyma, 

 the only distinction being that the angles formed by basal and lateral rays, which are in the 

 last named spicules usually of 120°, and if varying showing an inclination to grow more 

 acute, here in the dermal triradiate spicules show on the contrary an inclination to grow 

 more obtuse, varying from 120° to 125°. 



Stout acerate spicules. — Spindle-shaped, either straight or slightly curved, reaching 3 mm. and 

 more in length, the average proportion between the length and thickness being 30 : 1 ; 

 piercing the parenchyma in an oblique direction, the oral angle formed by them and the 

 longitudinal axis of the Sponge varying from 60° to 45°. 



Slender acerate spicules.— TLithuv spindle-shaped or more or less cylindrical, straight ; surface 

 either smooth or rather rough ; average size, 08 mm. by - 0025 mm. 



Colour. — Dirty white. 



Habitat.— Station 75, July 2, 1873; lat. 38° 37' N., long. 28° 30' W.; oft' the 

 Azores ; depth, 450 fathoms ; sand. 



Leuconia ovata, n. sp. 



I have already taken occasion to express in this paper 1 my assurance that the genus 

 Leuconia, as I restricted it, is a temporary one, and that its subdivision into main 

 quite independent genera can be predicted. The statement was also made, that one 

 of these conjectural genera will embrace forms like Leuconia saccharata, H., Leuconia 

 ochotensis, M.M., &c. The name of this new genus would be — according to the law of 

 priority — Baeria, Milducho-Maclay, and its chief characters a strongly developed cortex 



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