REPOET ON THE MONAXONIDA. 15 



This genus was first defined within its present limits hj Schmidt.^ Here, as in the 

 case of other Eenierinfe, it is impossible to give an absolute diagnosis separating it 

 from other genera, but no one who has studied the group will fail to recognise the fact 

 that it is a very natural genus. By the development of more spongin uniting the 

 spicules this genus appears to have given rise to those Chalinine sponges which possess 

 a definite rectangular skeleton, the fibre of which is cored by few and small oxeote 

 spicules, e.g., Chalina (s. str.). 



We cannot agree with Schmidt in referring those species which have a separable 

 dermal membrane (" zusammenhiingende Oberhaut") to a distinct genus, Pellina, as 

 we do not regard this character as being of generic importance. His original t3rpe of 

 Pellina is Reniera semituhulosa, Schmidt. The so-called dermal membrane is also 

 a very distinct feature of Halichondria panicea, yet Schmidt keeps this species 

 out of his genus Pellina, into which it ought certainly to fall according to his 

 definition, if such it can be called.^ 



Reniera cinerea. Grant, sp. 



1827. Spongia cinerea, Grant, Edin. New Phil Journ., vol. ii. p. 204. 



1828. Halichondria cinerea, Fleming, History of British Animals, Edinburgh, p. 521. 



1866. Isodietya cinerea, Bowerhank, Mon. Brit. Spong., vol. ii. p. 274 {vide also vol. iii. pi. xlviii.). 



We identify with this species a single small, massive specimen from Station 209, 

 measuring only about 12 mm. in diameter, and of a pale yellow colour. The spicules 

 measure about 0"14 by 0"008 mm. In connection with this specimen the remarkably 

 high temperature (71°'0) of the water in which it lived is very noteworthy. 



XocaZiVy.— Station 209, January 22, 1875 ; lat. 10° 14' N., long. 123° 54' E.; 

 Philippine Islands; depth, 95 fathoms; bottom, blue mud; bottom temperature, 7l°"0. 

 One specimen. 



Habitat. — British Seas (Grant, Bowerbank, &c.) ; Philippine Islands (Challenger). 



Reniera implexa, Schmidt, var. (PL I. fig. 4). 



1868. Reniera implexa, Schmidt, Spong. d. Kiiste v. Algier, p. 27. 



This species is well represented in the collection by a series of specimens from the 

 Azores. These, though identical in external form (PI. I. fig. 4) with Schmidt's species, 

 as shown by comparison with specimens in the British Museum from Trieste, purchased 

 from Professor Schmidt, difier slightly from it in skeletal characters. Thus the oxeote 

 spicules are a little longer and more slender in the Challenger variety, measuring about 

 0'16 by 0'0063 mm. as against about 0'138 by 0-007 mm. This difierence is but very 

 1 Spong. Atlant. Gebiet, p. 39. 2 Spong. Atlant. Gebiet., p. 41. 



