Echinoderrnata. 



which communicates directly with the exterior and corresponds to the canal system 

 of the sponges. Water enters by the ciliated pores on the disc and is driven out 

 by powerful muscles through pores at the syzygies in the arms, the currents thus 

 produced serving the purposes of nutrition and respiration. 



Carpenter ( 4 ) points out that some Crinoids (Holopus and Bathycrinus] have 

 no syzygies in the arms ; while there are no pores at the syzygies of any stalked 

 Crinoid. He further denies that they open externally in those Comatulae in which 

 their presence is apparent in the skeleton, and points out that the position of the 

 powerful muscles described by Perrier as expelling water through these pores, is 

 that of the radiating ridges on the syzygial faces which are the densest parts of 

 the calcareous tissue. Perrier's comparison of a Criuoid to a sponge will therefore 

 not hold good. 



Hinde describes a Palaeocrinoid with pitted tubercles on the calyx which have 

 articulated spines. [See Bericht for 1884 I p 180.] 



Wachsmuth & Springer publish numerous important observations on the mor- 

 phology of Palaeocrinoid s under the following heads : 1 . The Basals and Under- 

 basals. 2. The Radial and Arm Plates. 3. The Interradial, Interaxillary, and 

 Interbrachial Plates. 4. The Anal Plates and Anal Tube. 5. The Summit Plates. 

 6. The Ventral Perisome. The presence of under-basals in the calyx is not a 

 variable character, but is always associated with certain peculiarities in the orien- 

 tation of the stem and its cirri. When the basals are trimerous, the smaller plate 

 is always situated between the anterior and left anterolateral ray, whereas in the 

 Blastoids it is between the anterior and right anterolateral ray. The deltoid plates 

 of the Cyathocrinidae and the Blastoids are not oral plates as formerly supposed, 

 but calyx-interradials homologous with those of Platycrinus and other Palaeo- 

 crinoicls. The orals of Haplozrinus, Allagecrinus, and Coccocrinus are also really 

 interradials, though this is denied by Carpenter ('). Interradials occur in all Pa- 

 laeocrinoids being more extravagantly developed in the earlier groups, and extend 

 right up to the proximal dome-plates, sometimes covering them completely. The 

 views of Carpenter (*) are adopted with respect to the homologues inPalaeocrinoids 

 of the anal appendage of Thaumatocrinus . His suggestions as to the homologies of 

 the summit-plates [see p 187], are criticised in detail. The central plate is not homo- 

 logous with the dorsocentral of the abactinal side, but represents five anchylosed 

 orals [= basalsi ; while the proximals are the homologues of the calyx-interradials. 

 The mouth and ambulacra were closed in all Palaeocrinoids, Coccocrinus included. 



Hambach f 1 ) reaffirms his previous statements respecting Blastoid morphology 

 which had been questioned by Carpenter [Bericht for 18801 p254; 1881 I 

 p 193]. The ambulacral pores give passage to tentacles connected with the 

 hydrospires ; and the so called summit-plates are only accidental coverings to the 

 mouth. The various species of Pentremites which do not belong to Cadaster or Codo- 

 nites can be classed, according to the characters of the spiracles, in three groups, 

 the types of which are P. sulcatus, P. melo, and P. Nonvoodi. Carpenter ( 2 ) cri- 

 ticises the theories of Hambach respecting the summit-plates and ambulacral cover- 

 ing plates of the Blastoidea, pointing out that both are natural and not accidental 

 structures. The supplemental pore-plates are regular limestone-plates, and not 

 collapsed tentacles as asserted by Hambach, for tentacles did not exist in con- 

 nection with the hydrospires. 



Wachsmuth (*) finds that the supposed supplemental basals of the Blastoids are 

 non existent. In Cadaster, Orophncrinus, Troostocrinus and other forms with an 

 elongated basal cup, it is marked by an apparent suture owing to the more rapid 

 spreading of its upper portion, but it is not really dicyclic. In Pentremites the sup- 

 plemental basals consist merely of a stem-joint anchylosed with the basals and 



