REPORT ON THE HEXACTINELLIDA. 155 



be that three, or less frequently five, boss-like projections remain, which correspond in 

 their position to the undeveloped rays (PI. LIX. fig. 14). 



The gastral skeleton is unfortunately not preserved, and this fact may make it 

 somewhat doubtful whether I am correct in regarding this form as a thin-walled 

 Bathydoriis, and not as a representative of a genus Rhahdocalyptus, now to be 

 described. 



Genus 6. RJiahdocalyjJtus, n. gen. (Pis. LXIV., LXV.). 



The body has the form of a moderately thick-walled cup or sack, with smooth 

 external surface. It is attached by a narrowed base or short stalk to a solid body. 

 The wide round oscular opening has a gradually sharpened smooth margin. The 

 interior surface exhibits, between the close round excurrent apertures of the numerous 

 efiierent canal or lacunar passages, an irregular ridged network. 



The principal pareuchj'mal spicules are more or less long diacts. Besides disco- and 

 oxyhexasters of various sorts, eight-rayed rosettes occur, with several disc-bearing 

 terminal rays borne on the end of each medium-sized principal. 



The dermal membrane contains either only rough diacts, or also rough pentacts, 

 tetracts, and monacts. The gastralia are rough oxyhexacts. 



1. Rhahdocalyptus mollis, n. sp. (PI. LXIV.). 



Among the dried Japanese Hexactinellids which Dr. Doderlein collected near Enoshima, 

 the form figured in PL LXIV. fig. 1 (one-third natural size) is conspicuous because of 

 its large dimensions. It is a moderately thin- walled, laterally compressed cup, 35 cm. 

 in height and 20 cm. in breadth at the superior aperture. The diameter of the round 

 compact stalk is about 6 cm. The large cup bears on its side a smaller, more elongated 

 form, 15 cm. in length, and 6 cm. in width at its orifice; while beneath the latter there 

 is a csecal protrusion or boss. 



The wall, which measures in its lower portion 4 to G mm. in thickness, becomes 

 gradually thinner towards the upper end, and terminates in an undulating or crisped, 

 smooth, slender, oscular margin, without a fringe of spicules. At the lower portion of the 

 cup, just above the solid, somewhat tuberculated base, there is a round hole, 5 mm. in 

 diameter, which establishes a communication between the gastral cavity and the water 

 outside. The stalk is attached to the firm substratum by a slight basal expansion, 

 and includes here and there some intruded material, especially soil debris. The lower 

 surface of the stalk, where it is fixed to the substratum, exhibits the familiar thin but 

 firm reticulated plate, which is developed in all Hexactinellids at their point of attachment 

 to foreign bodies. The outer surface of the body is not quite uniformly curved, but exhibits 



