REPORT ON THE HEXACTINELLIDA. 303 



photograph. It has the form of a slender cup, attached to a broad basal plate, and is 

 12 cm. long by 4 broad in its upper portion. It is not, however, intact. Since Sir 

 Wyville Thomson speaks of two specimens from this locality, of which the larger was 

 17 cm. in length, it is evident that the latter is not in the collection before me. 



In Wyville Thomson's description, and in fig. 1 on PI. LXXIL, attention is directed 

 to the oblique or transverse lidges projecting on the external surface of the cup and 

 alteruatino- with somewhat broader erooves. These transverse ridges consist almost 

 wholly of a row of closely apposed and externally fused, short tubular stumps. The 

 circular external end measures 4 to 5 mm. in breadth, and is directed radially outwards. 

 In the grooves, on the other hand, there are numerous, irregularly arranged, round or 

 elongated, oval openings of variable size, which lead into more deeply situated ducts. 



The internal gastral surface of the cup presents another appearance. Here one ob- 

 serves a number of longitudinal ridges from 2 to 3 mm. in breadth, which project inwards 

 and are separated by deep longitudinal grooves of equal breadth. Since these longi- 

 tudinal ridges with arched roof extend from the lower blind end of the slender cup-shaped 

 gastral space to the upper, and here and there part, their number gradually increases from 

 below upwards, and in the upper broken end amounts to twenty. Each of these longi- 

 tudinal ridges consists of two plates, which pass into one another at the free inner 

 edge, and thus enclose an elongated slit-like space. Internally this is shut off from the 

 gastral cavity by the skeletal fold referred to, while it communicates externally 

 with those cavities and clefts which occur at the foot of the external transverse 

 grooves. From the longitudinal furrows, however, which occur on the internal surface 

 of the cup between the gastral ridges, there is a direct communication into the lumen of 

 the tubular stumps which project radially on the external transverse ridges. When this 

 is compared with the structure of the not very remotely allied Perijihragella, it seems 

 clear that the lateral tubular stumps of the outer transverse ridges, whose cavities com- 

 municate directly with the gastral cavity and w^hich project radially outwards, represent 

 the efferent lateral tubes of Periphragella, and like the large oscular terminal aperture of 

 the whole cup serve for the exit of the water, while the apertures and cleft lying in the 

 external transverse grooves, together with the associated, but internally closed, longi- 

 tudinal ducts or slits, belong to the afferent system. 



The dictyoual framework consists of smooth beams enclosing predominantly square or 

 rectangular meshes, without thickening of the nodes of intersection. The freely projecting 

 conuli are on the other hand beset with tubercles and teeth. 



In the compact portions of the lattice-work, a few isolated spicules here and there 

 occur, but it is, of course, doubtful whether they really belong to Lcfroyella decora or 

 are only intrusions. I have, therefore, simply mentioned their occurrence without giving 

 any figure. Besides simple, smooth hexacts of small size and uncinates of medium length, 

 there are scopulai with four straight, terminally knobbed prongs. 



