ECHINOIDEA 815 



it may be reduced to inconspicuous partition walls at the edge 

 of the test, or it may be almost totally wanting. Ambulacral 

 plates simple ; on the upper side the ambulacra are usually 

 widened ("' petaloid ''), forming a flower-like figure. Dental 

 apparatus strongly developed. Tubercles perforate. Spines 

 quite small, forming a close, almost velvet-like coat. Tube-feet 

 small, usually many to each ambulacral plate and often spreading 

 also over the interambulacra. Pedicellarise small and incon- 

 spicuous, mostly only tridentate, ophicephalous, and triphyllous. 

 Sphseridia present, but placed in grooves in the test so as not 

 to be externally visible. 



This order is richly developed in tropical seas, but has in 

 recent times only a single representative in European seas, 

 whereas numerous fossil (tertiary) forms are known, especially 

 from the deposits of the Mediterranean countries. 



T. Family Fibulariid.e 



Test usually elongate, flattened or arched. Internal supports 

 of test feebly developed, consisting only of small radiating 

 partition walls at the edge of test, or even almost wholly 

 wanting. Ambulacra only shghtly petaloid on upper side. Anal 

 opening on under side of test. Very small forms. 



Only one genus in the British (and European) seas.^ 



1. Echinocyamus (van Phelsum) Leske. 



Test usually elongate, flattened ; internal radiating partition 

 walls present, bounding the ambulacra. Numerous very small pores 

 (and tube-feet) along the horizontal sutures between the ambu- 

 lacral plates. Only 1 pore in the madreporite. Four genital pores. 

 Spines of two sorts, somewhat longer, pointed ones, and smaller 

 ones ending in a serrate crown. 



Only one species, Ecli. j^usiUus, known from the British seas, 

 but two more species may well be expected to occur there like- 

 wise, namely Echinocyamus grandiporus Mrtsn., known from off 

 the Azores and from the Josephine Bank, also widel}^ distributed 

 in the West Indian seas, ca. 150-1385 m. ; Echinocyamus macro- 

 stomus Mrtsn., known from off the Azores and Cape Verde, 1600- 



^ The record of Arachnoides placenta (Linn.) from the Shetland Islands 

 (Forbes) is evidently erroneous ; this species, therefore, should no longer 

 be named, even with reservation of doubt, in any record of British 

 echinoderms. 



