BY R. VON LENDENPELD, PH.D. 1143 



52. SPECIES. EILHARDIA SCHULZEI. Pol(5jaeff (1.) 



The concave surface is dull, the convex has a silvery lustre. 

 The convex surface bears low volcano-like Oscula, disposed at 

 approximately equal distances, one from another ; their diameter 

 does not exceed 0"4 mm., usually being still less. The concave 

 surface may be compared to a seive, its pores inconspicuous to 

 the naked eye, are found under the microscope to be round and 

 disposed close together; their average diameter is 0-06 mm. 

 The wall of the calyx 3 mm. to 7 mm. thick near the centre, 

 grows gradually thinner towards its free blade-like margin. 



Skeleton. The skeleton of the sieve-like surface consists of 

 sagittal Triradiate and minute Acerate spicules; that of the 

 Parenchyma, of large regular, often sagittal Triradiate, and of 

 minute acerate spicules ; that of the convex Oscular surface of 

 large acerate and subdermal triradiate ; that of the Oscula them- 

 selves of an exterior layer of large acerate, of a middle layer of 

 sagittal triradiate, of an inner layer of quadriradiate, and of 

 minute acerate spicules, supporting the ring-like border of the 

 external opening of the Osculum. The minute acerate spicules 

 are in all parts of the body of the Sponge of the same outline. 



Minute Acerate Spicules. Usually 0-05 mm., long, with a 

 diameter of 0*0025 mm. Triradiate Spicules of tho Sieve-like 

 surface. Sagittal ; all rays lying in the same plane, of the same 

 diameter, tapering from the base to approximately sharp points ; 

 lateral rays curved forwards, slightly undulating, each forming 

 with basal ray an angle varying from 115° to 120'*, reaching 

 75 mm., in length, usually not longer than 0-5 mm., often still 

 shorter the proportion between the length and the thickness being 

 15:1 ; basal ray straight, length inconstant, either rather exceed- 

 ing that of lateral ray or equal to it, or even less. 



Triradiate Spicules of the Parenchyma. Regular, with pro- 

 nounced inclination to sagittal differentiation by the shortening of 

 basal ray ; all rays of the same diameter ; the proportion between 

 their length and thickness varying, in lateral rays, from 10:1 to 



1 .) ^V. PoUjaeff. L.c, p. 70, pi. 11. , fig. 7 ; pi. IX., fig. 1-70. 



