CARADOCIAN CYSTIDEA FROM GIRVAN. 



439 



demirhombs 1-4, 1-2, are constant, now proves incorrect. Jaekel (1899, p. 217) had 

 already described the demirhombs as only " haufig," but did not say from which 

 species they were absent. It might be inferred from his description (p. 221) that they 

 were absent from C. alter, but they are represented in his plate 11, f. 8. At any rate 

 they are not developed in C. constrictus. That species, moreover, is peculiar in having 

 no rhomb 1-6. 



I 299. Perhaps the most general statement that can be made is that, in one or 

 other species of Cheirocrinus, rhombs may occur in any of the positions shown in 



J6^ 



"VJ- 



\18i 



Alius 



14 ^ 



/ \\^^ 



"w p^ 



^y/f^ 



r m 



'"13'-'' 



w/M 



^lOj 



■^-'"^ 



•^-'-'S^ 



CrtTv^ 



s A 



"'Anus 



14 



Texi-fig. 45.— The actual distribution of all pore-rhombs knowu with certainty in the Glyptocystidea, 

 showing how a space is left clear where the gut may be supposed to press against the thecal wall. 

 iV.5. — This diagram is a corrected edition of that published in Bather (1900). 



f. 20 on p. 58 of the "Treatise" (1900), with the addition of 5-6 and 11-12, both of 

 which are represented in Jaekel's analysis of C. radiatus (1899, p. 213). These 

 additions, as may be observed in the accompanying diagram thus altered, do not block 

 the track represented as made clear by the pressure of the gut (text-fig. 45). 



Conjunct. Disjunct. Multidisjunct. 



Text-fig. 46.— Pectinirhombs of Cheirocrinidae. 



^ 300. Miss Wood (1909, p. 7) states that in C. angulatus "pectinirhombs are 

 present ... on plates L 1 to L'2 and L2 to L'2," i.e. 6-1 1 and 5-11. Both these positions 

 are unparalleled in the genus, so far as our knowledge goes. The unique specimen 

 unfortunately is very imperfect, and may present difficulties of orientation. 



§ 301. The rhombs may have the folds continuous across the suture (Vollrauten, 



conjunct rhombs), or interrupted above and on each side of the suture by a bridge of 



stereom (Sperrauten, disjunct rhombs ; text-fig. 46). Conjunct rhombs are found in 

 TRANS. ROY. SOC. EDIN., VOL. XLIX. PART II. (NO. 6). 58 



