120 BRITISH PALvEOZOIC ASTEROZOA. 



Ambulacralia with but slight or no carination are described by Schuchert for 

 Hudsonaster narrawayi (1915, p. 59) and Anorthaster miamiensis (1915, p. 126). 

 Reduced adambulacralia are found in Urasterella (see below, p. 148) and Calli- 

 asterella (p. 167). It is obvious that a reduction of the ambulacralia in functional 

 importance can occur in many different genera. 



The infero-marginalia at the extremities of the arm are globular and swollen. 

 Their disposition with respect to the ambulacralia varies in the different arms. 

 Thus at the end of arm iv the infero-marginalia are equal in number and opposite 

 to the ambulacralia. In arm x the distal infero-marginalia are slightly less 

 numerous than the adambulacralia and consequently alternating (roughly there are 

 four adambulacralia to three infero-marginalia). The infero-marginalia of this 

 portion of the arm are on the lateral rather than the oral surface, but as we 

 approach the base of the arm the infero-marginalia become flat and closely fitting. 

 They also pass over on to the oral surface. They are always equal in number to 



74 

 73 



$ O p& 



Text-fig. 73. — Wash drawing of an adambulacral of Lepidaster grayi to show ornament, x 12. 

 Text-fig. 74. — Wash drawing of the madreporite of Lepidaster grayi. x 6. 



the adambulacralia, and each infero-marginal articulates with an adambulacral 

 exactly as do the ventro-lateralia with the proximal adambulacralia (see above). 

 The infero-marginalia at the exact base of the arm are squamiform. In the inter- 

 radius between arms v and vi they are continued as an arc round the axil of the 

 arm, but in the madreporite and other interradii they are more broken up and 

 there is an appearance as if they were trying to thrust themselves into the disc. 

 Displaced squamiform supero-marginalia may be seen in the interradii between 

 several arms (see also below). 



The Sedgwick Museum Specimen is incomplete. The appearance of the arms 

 which have been preserved is much as in the Jermyn Street specimen. 



The Dudley Specimen (Plate VII, fig. 6; Text-figs. 73, 74-). — This specimen is 

 almost exactly the size of the holotype. The disc was folded before preservation 

 in such a way that an oral view of eight arms is obtained, the remaining arms 

 being mostly in apical view. Although this allows valuable apical views not seen 

 in other specimens, the disc is so effectively hidden that only the free portions of 

 the arms may be observed. Their structure is exactly as in the Jermyn Street 

 specimen. The whole surface of the form is pitted just as if originally it were 



