SCHUCHERTIA LAXATA. 



213 



Specific Characters. — See p. 211. 



Oral Surface (Text-figs. 152, 15:]).— For comparison with the British specimens 

 I have reproduced Schuchert's original figure, in which both the odontophor and 

 the proximal infero-marginalia are very distinct, The mouth-angle plates are 



Text-fig. 151. — Drawing of a portion of the apical surface of Schurfiertia laxata? R., radialia. x 6. 



drawn with a wide gape, and are apparently preserved much in the same position 

 as they are in the specimen of S. ivenloclci, figured PI. XV, fig. 3. D. 331 shows a 

 pair of similar mouth-angle plates, but here the muscle occupying the gape had 

 contracted before death, and the gape is scarcely visible. The odontophor is as in 

 the American specimen. The interradial area in the American specimen is 



MR' 



Am. 



Text-fig. 152. — An interradial area and the ambulacra! groove of Schuchertia laxata (after Schuehert). 

 Ad., adambulacral ; Am., anibulacral; Ir., interradial plates; M.P., month-angle plate; 0., odontophor. 

 x 4. 



occupied by numerous small plates described by Schuehert as " smallest in the 

 inner axillary areas and thence increasing rapidly to a size maintained throughout 

 the interbrachial areas. In form they are either diamond-shaped or subquadrate, 

 centrally tumid, and each plate seems to have borne one central and two or three 

 lateral spines." D. 332 shows similar plates perhaps just a little larger than in 

 the American figured specimen. They merge gradually into the apical skeleton. 



29 



