98 



FOSSIL ASTEROIDEA. 



of the majority of the marginal plates. The type is the specimen figured in Text- 

 fig. 2. 



Description. The abactinal area of the disc is covered with hexagonal plates, 

 which have a distinctly stellate appearance on their upper surface. 



The arms are distinctly produced. In the specimen figured in Text-fig. 1, 

 R : r : : 41 mm. : 28 mm. In the specimen figured in Text-fig. 2, R : r : : 41 mm. : 



TEXT-PIG. 1. 



TEXT-FIG. 2. 



TEXT-FIG. 1. a, Abactinal view of a specimen of M. quadratus, nat. size; fc, actinal view of the 



same specimen ; c, view of infero-marginal plate magnified two diameters ; d, view of two 



supero-marginal plates magnified two diameters. 

 TEXT-FIG. 2. a, Abactinal view of another specimen of M. quadratus, nat. size; 6, actinal view of 



the same specimen ; c, view of infero-marginal plate magnified two diameters ; d, view of two 



supero-marginal plates magnified two diameters. 



30 mm. The length of the side in the first-named specimen is 51 mm., in the 

 second-named specimen 56 mm. 



The supero-marginalia are either five or six in number, counting from the 

 median inter-radial line to the extremity of the arm. In the inter-brachial area 

 they are distinctly quadrate in character, and are from 7 to 8 mm. in width and 

 from 6 to 7 mm. long. 



The terminal paired supero-marginalia present very curious features. In 

 the specimen figured in Text-fig. 1 some of these plates are large and tri- 



