42 The Ottawa Naturalist. June-July 



haps more abundant forms living on the bottom. The collect- 

 ing apparatus consisted of numerous small brachioles or pin- 

 nules which captured the living organisms by means of ciliated 

 grooves, lined with viscous secretions, and protected by a series 

 of minute alternating cover-plates. The material caught by 

 brachioles or pinnules was passed into common covered ways 

 leading to the mouth. The main streams became in time mere 

 conduits, and the surplus water taken in with capture and used 

 for conveyance was either gradually lost between the cover- 

 plates or carried to specialized separating areas, where the water 

 was sent to hydrospires and made to assist in respiration. With 

 this manner of food getting it will readily be seen that the cover- 

 plates nearest the mouth would tend to remain closed and to 

 become permanently fixed, or the proximal portions of the food 

 grooves might become subtegminal in position. In every case 

 the extent of the collecting portion of the apparatus is pro- 

 portioned to the needs of the organism, and to the abundance 

 of minute organisms in its habitat. Deprive Crinoid, Blastoid, 

 Parablastoid or Cystid of its pinnules or brachioles, and its 

 larger or main covered food-grooves could no longer function. 

 Now, we must ask ourselves these questions. If the Edrio- 

 asteroidea are Cystids they belong to a group that secured their 

 food by means of brachioles ; they were for the greater part fixed 

 and sessile forms, and could therefore only feed on such passing 

 organisms as they could capture; for their size they show no 

 greater length of covered food-grooves than we find in Malo- 

 cystites, which was an elentherozic form and a feeder close to 

 the sea bottom. Why should the Edrioasteroidea have lost 

 the inheritance of the collecting mechanism of their class, and 

 how could they secure sufficient food without it? These are 

 serious questions, and they are made no easier by raising the 

 group to class rank, for even then every other class of their sub- 

 phylum required and retained the fringing brachioles or pin- 

 nules. 



If we compare Blastoidocrinus with Steganoblastus, the 

 need for and probable possession of brachioles by the latter 

 will become more evident. Both are stemmed forms, with 

 similarly shaped body cavities, and with proportional surface 

 areas, covered by large food-grooves. In Steganoblastus, a 

 name suggested by Bather on account of the closely covered 

 condition of the main food-grooves (1914, p. 193), we find 

 "large covering plates," (loc. cit.) which form a prominent 

 rounded arch over the groove" (1914, p. 200). "At the proxi- 

 mal end smaller plates may be intercalated along the middle 

 line" (19-1-4, p. 199, and fig. 5, p. 200), or "the medial suture 

 in the proximal region becomes curved and interlocking" (1914, 



