REPORT ON THE TETRACTINELLIDA. 
335 
Remarks. — The fragments which I received from Professor Agassiz, and which are 
now, by his permission, placed in the British Museum, were parts of the dead skeleton 
of the sponge, so that I am not able to supplement Schmidt’s description with an 
account of the smaller spicules. 
The resemblance of the desmas to those of the fossil Siphonia (in which we suppose 
Jerea to be included) is much closer than in the case of Neosiphonia super stes. A 
similar resemblance exists in the outer form and the general arrangement of the canal- 
system, so that with much plausibility we may regard Neosiphonia as a lineal descendant 
from the Mesozoic Siphonia. 
The additional localities for the sponge were kindly communicated to me by Mr 
Walter Fewkes, who states that all the specimens, of which there are four, are “ dry.” 
This confirms my impression that they are also deciduous. 
Genus 5, Rimella, 0. Schmidt. 
Generic characters partly included in the description of the single species, partly 
unknown. 
Rimella clava, 0. Schmidt. 
Rimella clava, 0. Schmidt, Spong. Meerb. Mexico, p. 21, pi. i. fig. 2, pi. ii. figs. 5, 7, 11, 1879. 
Sponge. — Small, more or less clavate, attached by a flat expanded base, growing out 
at regular intervals on alternate sides into protuberances, which may enlarge into short 
branches ; the soft parts being removed, a number of somewhat deep longitudinal 
furrows are seen descending from the summit of the sponge to the lateral protuberances, 
and from them to the base. 
Spicules. — I. Megascleres. 1. Desma, various in form, sometimes regularly tetra- 
cladine, sometimes wholly irregular, bearing large tubercles, which are not confined to the 
ends of the cladi, but extend over their sides, frequently up to the actinal centre, often 
confined to one side of a cladus. The tubercles when fully grown present a short 
cylindrical pedicle, constricted in the middle, so that the sides are concave in outline ; and 
an expanded cushion-like tylus, which is sometimes faintly lobed ; height of the tubercle 
0'039 mm., diameter of the pedicle 0’032 mm., of the tylus 0'045. The axial fibre of the 
crepis seldom exceeds 0’09 to 0T15 mm. in length, while the total length of an epactine 
and cladus is usually 0’23 to 0'32 mm.; in one or two instances only was the axial fibre 
observed to extend to the extremity of an epactine, which in this instance measured 0T9 
mm. in length. In another instance the fibre was seen to dichotomise at the end of 
the epactine where the protocladi originate ; the axial fibre of the epactine measured 
0‘084 mm., of the protocladus 0'013 mm. in length. Zygosis occurs not only at the 
