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from the Lower Silurian of Rohemia, which he thinks must be a fossil 

 Crinoid-larva ("cin IMuUnis oinos Crinoiden"), the "f'^iira bohemicn' of 

 Barrande'). liul provided lirsl Ihat it be an Echinoderm, anybody who 

 has the slightest knowledge of Kchinoderm-larvcT will see at a glance that 

 it is quite absurd to speak of a iarva" in a case like this, where a single 

 or double series of distinct marginal plates is represented along the whole 

 border of Ihe animal. Hut, moreover, it is certainly no Kchinoderm al all. 

 Professor (). .laekel, with whom 1 have discussed this mailer, informs me 

 thai he knows the 'Furcd bolwinica" quite well, and stales that Ihe re- 

 presentation which Frilsch lias given of it is quite erroneous. In fact, 

 Professor .laekel does nol hesitate in declaring it to be identical with 

 the organism from llic Middle Cambrian (Stephen formation) of British 

 Columbia which Walcoll has described-) under the name of Marella 

 splt'iulcns, and which is a C.iustacean, probably allied to the Trilobites. 



As regards the anatomical sliuclureof theEchinoderm-larvse ( — leav- 

 ing the reduced, barrel-shaped forms out of consideration here — ) attention 

 may be called to the fact that the ventral depression of the body, in which 

 the mouth lies, the oral area, generally continues some way down below 

 the upper edge of the anal area, thus forming a cavity, the lower hmil 

 of which is mostly very distinctly seen as a line passing across the anal 

 area at aboul the level of the lower end of the esophagus. It is sometimes 

 very large, as in Opliioplulcus scridliis (bimnciilalus), sometimes also of a 

 more comj)licale shape, as in the larva of Colobocenlrolus atralus. This 

 "suboral cavity", as I have termed it, was well figured and described by 

 .loh. Miiller in his Memoir "Cbcr die Ophiurenlarven d. Adriatischen 

 Meeres", p. I, Taf. I, Fig. 1, and also Metschnikoff (Op. cil.) has care- 

 fully studied this cavity, the ■"subumbrella" as he names it. in the same 

 larva, where it plays an imporlnnl part during the process of metamor- 

 ])hosis. Also in a Spatangoid-larva he has noticed it (Taf. VIII, Fig. 12). 

 The same structure was observed, but apparently not understood, by Mac- 

 Bride in the larva of Evhinocaidium conUdum: he only mentions it as 

 "two large cavities", one on each side in "the web of skin connecting the 

 post-oral arms." — This cavity has some connection with the (|uestion 

 about the origin of the ■amnion" of Echinoid-larvje, and accordingly some 

 morphological interest is attached to it. 



In the e|)idermis of Ihe sunk oral area is found a pnii' of ii eive-st reaks. 



') A. l-'ritscli. I'ber ciiu' i;cliinoiloriiu'iilarve aus deiii I'nlersilur Boliinens. Zool. Anz. 

 X\. 1909. p. 797. 



-) Cli. I). Wakolt. Cainl)rian (leolotiy and I'aleontology. II. N'o. 6. Middle Cainhrian 

 Branchiopoda, .Malacostraca. Irilobita. and Merostoniata. Smiths. iMiscell. Coll. Vi>l " 

 1912. p. 192. PI. 2.". —26. 



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