L E PI D ASTER. 123 



Measurements. — The holotypehas R : r : : 51 mm. : 22 mm. (R = 2.3 r). Length 

 of free portion of arm is 27 mm. 



Dudley Museum specimen : Length of free portion of arm is 27 mm. 



Jermyn Street specimen has R : r : : 34 mm. : 14 mm. (R = 2 - 4 r). Length of 

 free portion of arm is 20 mm. 



Sedgwick Museum specimen, R : r : : 23-2 mm. : 9-3 mm. (R = 2'5 r). 



Birmingham University specimen, R : r : : 145 mm : 5 - 5 mm. (R = 26 r). 



There is evidence, therefore, that the disc increases more rapidly than the 

 arms as the form becomes more mature. 



Horizon and Locality. — Middle Silurian (Wenlock Limestone) of Dudley, 

 Worcestershire . 



Trichotaster plumiformis. — The Grindrod Collection is stated by Wright to have 

 contained a small ten-armed form from the same locality and horizon, which he 

 named Trichotaster plumiformis. The specimen appears to have been very badly 



.m: 



Text-fig. 78. — Cross-section through an arm of the Jermyn Street specimen of Lepidaster grayi. 

 Ad., adambulacralia ; I.M., infero-marginalia. x 6. 



preserved, and it was not figured, but the original description is as follows : " The 

 specimen described showed the outlines of a small starfish, with a large disc and 

 short rays, in a slab of Wenlock Limestone from Dudley. The outline of the ten 

 rays was described as marked out by the border of small triangular spines, the 

 other plates of the disc and rays being absent. Each ray was terminated by a 

 stem-like multi-articulate process as long as the ray, from towards the extremity 

 of which spring slender lateral processes, giving it a tufted appearance." I have 

 not seen the specimen, but the locality in which the specimen was found, and the 

 fact that Lepidaster is the only pre-Devonian multi-rayed starfish, suggest that 

 Wright's species, like the Birmingham University specimen, is an immature 

 example of Lepidaster grayi. 



Mode of Life of Lepidaster. 



Some time ago, when thinking over the structure of Lepidaster, I came to the 

 conclusion that it was not a predatory form like most of the Asteroidea, but that it 

 was sedentary and sat with its apical surface on the sea floor Avhilst its arms were 



