The Skeleton and Classification of Calcareous Sponges. 73 



little reason for supposing Calcarea to be a natural class ; but 

 retaining it provisionally I propose to divide as follows : 



Class. CALCAEEA. 

 Sub-Class I. Calcaronedy nov. 



The nucleus of the collar-cells and of the flagellate cells of the 

 larva is distal, and the flagellum arises from it directly. The larva 

 is an amphiblastula. The first spicules to appear are oxea, generally 

 (always ?) lance-headed, the triradiates are typically alate* and 

 the optic axis is rarely perpendicular to the plane of the spicule. 

 The pylocyte is annularf and generally lies at the bottom of a 

 funnel-shaped depression or afferent canal. Branching of the 

 sponge takes place typically nearly at right angles to a growing 

 axis, giving rise to stolonate and arborescent forms. The gastral 

 fourth ray of a quadriradiate spicule rarely rises perpendicularly 

 from the meeting point of three rays. Lance-headed oxeotes are 

 frequently present in the adult. The sponges never show a coral-red 

 or sulphur -yellow colour. 



Order 1. Asconida, H. (s.m.). The central cavity is in the adult 

 lined with collar-cells and communicates with the exterior directly 

 by pylocytes in its walls. 



Fam. LeucosolenidoK, Minchin. Genus 1. Leucosolenia^ Bwk. emend. 

 Minchin. Genus 2. Ascyssa, H. 



Order 2. Sycettida, nov. The central cavity is in the adult not lined 

 with collar-cells and does not communicate with the exterior directly 

 by pylocytes in its walls. 



Fam. 1. Sycettidce, Dendy. 



,, 2. Qrantidce, Dendy. 



,, 3. Heteropidce, Dendy. 



,, 4. AmphoriscidcR, Dendy (s.s.). 



Sub-Class II. Calcined, nov. 



The nucleus of the collar-cells and (? ?) of the flagellate cells of 

 the larva is basal, and the flagellum does not arise from it directly. 

 The larva is a parenchymula. The first spicules to appear are 

 triradiates, the triradiates are typically equiangular and the optic 



* I.e., with paired angles, from the resemblance of the oral rays of such spicules 

 to the two wings of a flying bird. [I propose the corresponding term " caudate" 

 for equiangular sagittal spicules.] 



f "Pylocyte" = the cell surrounding a prosopyle, leaving "porocyte" = the 

 cell surrounding a pore. I have observed this in Leucosolenia LieherJciihnii, Sycon 

 rapTianus, Si/con compressum, and Leucandra aspera. Cf. Dendy on Leucosolenia 

 stolonifera ((14), p. 25), and Granlessa iniusariiculata ((17), fig. CO), and PolejaeiF 

 on Grantia tuberosa ((17), pi. 3, fig. 7). 



