200 DE. HINDE AND MR. HOLMES ON SPONGE-REMAINS 



eannot be considered as the young or immature stage of the 

 melon-shaped spicule of the same species as supposed by Mr. Carter 

 (Spong. Mexico, p. 85). 



MelonancTiora Morlandi, n. sp. — PI. IX. fig. 38. Spicule oval 

 or melon-shaped in outline ; ends narrowly rounded, sides evenly 

 curved, and of about an even width, a regular well-marked sub- 

 circular inner notch at both ends, but none in the centre. Outer 

 margins smooth and even, the laminse gradually thinning to a 

 knife-like edge ; a definite axial canal extending quite round the 

 spicule just within the margin. Traces of transverse striae 

 across the walls. Length of spicule "IS mm., width -OS mm. 

 Thickness or width of the wall '018 mm. 



The character of this spicule may be understood if we sup- 

 pose the shafts only of two of the ordinary bihamate spicules of 

 Hamacantha, like those represented on PI. IX. fig. 33, placed 

 vis-a-vis, and welded into a single spicule, which would then 

 have the same outline, the same circular notch at the ends, and 

 the same knife-edge at the inner margin as the present fossil ; 

 further, if the canals in the Hamacantha spicules were connected 

 together they would also resemble the continuous axial canal of 

 the melon-spicule. As compared with the melon-shaped spicule 

 of the recent MelonancJiora elUptica, Carter (Ann. & Mag. N. H. 

 s. 4, vol. xiv. 1874, p. 212, pi. xiii. figs. 6-12, pi. xv. figs. 35 «, h), 

 the present fossil has the remarkable peculiarity that it only 

 includes one-half the recent form, for whilst the recent spicule 

 consists of two oval frames at right angles to each other, the 

 fossil possesses only one, and yet it has every appearance of 

 being complete. Beyond that the fossil is larger than the 

 recent " melon " spicule and has not the notch in the middle of 

 the inner margin, there is considerable similarity to the recent 

 form. It indicates a new species of the genus, w'hich may be 

 termed Melonanclwra Morlandi, in honour of Mr. H. Morland, 

 to whom we are indebted for the discovery of this spicule in the 

 Oamaru material. The skeletal spicules of the recent type 

 species of Melonancliora are, according to Mr. Carter, simple 

 acuatfes and tibiellas, of similar proportions to some of those in 

 the Oamaru material figured on Pis. VIII. and IX. The recent 

 species is only known from the North Atlantic and from the 

 Caribbean Sea (Spong. Mexico, p. 85, t. ix. fig. 8). 



