'370 THE VOYAGE OF H.M.S. CHALLENGER. 



To the Euplectellidse are also to be referred the following seven genera, which have 

 not as yet been sufficiently investigated. 



Genus 1. Hahroclictyum, Wyville Thomson. 



With the single species, Hahroclictyum speciosum (Quoy and Gaimard). 



Tubular forms with irregular parietal network, firmly attached by a knotted basal 

 portion. The lateral wall is directly continued without definite margin or cuff into the 

 uniform gently arched terminal cupola. The parenchyma contains oxyhexasters with 

 medium-sized principal rays and short terminals. Molucca Islands. 



Genus 2. Eudictyum, Marshall. 



With the single species, Eudictyum elegans, Marshall. 



The terminal sieve-plate is distinct indeed from the lattice-work of the tubular parietal 

 skeleton, but is not markedly different. The parenchyma contains small discohexacts. 



Genus 3. Dictyocalyx, n. gen. 



With the single species, Dictyocalyx gracilis, n. sp. 



A funnel-shaped skeletal network with altogether irregular meshes, firmly attached 

 to a substratum by means of a solid compact stalk. The parenchyma includes several 

 kinds of discohexasters, some of which bear on their terminal rays marginally toothed 

 convex discs, and others lacerate campanulate terminal umbels. South Pacific, 2385 

 fathoms. 



Genus 4. Rhahdodictyum, 0. Schmidt. 



With the single species, Rhahdodictyum delicatum, 0. Schmidt. 



A very lank almost tubular cup, borne on a small compact basal plate. The parietal 

 skeleton is traversed by round smooth holes, and consists of irregularly disposed long- 

 rayed hexacts which are cemented together. Bequia, 1591 fathoms. 



Genus 5. Rlmhdopectella, 0. Schmidt. 



With the single species, Rhahdopectella tintinnus, 0. Schmidt. 



A firmly attached cup with skeletal beams cemented together below, but consisting 

 superiorly of free and isolated spicules. The parenchyma contains the usual oxyhexasters, 

 and also other forms in which the strong terminal rays appear to spring from a central 



