512 CLYPEASTER SCUTIFORMIS. 



Clype aster scutiformis 



Echinus scutiformis Gmei... 1788, Linn. Syst. Nat. 

 ! Clypeasier scutiformis Lamk., 1816, An. s. Vert., p. 16. 



Pl.XIJF.f. 1-4, 



This small species would at first glance pass for an Echinanthus allied to 

 E. testudinarius. It presents even outwardly several peculiar features which 

 have led Desor and other authors to place it in the genus Laganum, on 

 account of its swollen edge and of the depressed abactinal part of the test 

 in some specimens. I have at one time considered it the type of a distinct 

 genus. Test depressed. The general outline is somewhat elongated, pen- 

 tagonal, with rounded angles, pointed anteriorly, and slightly re-entering 

 sides in the posterior interambulacral ; edge of test swollen. Petals extend- 

 ing to the inner line of the swollen edge of the test, the abactinal part of 

 the test frequently quite flat, or rising hut little towards the apex ; the 

 extremity of the poriferous zone of the petals somewhat concave ; the con- 

 cavity extending sometimes to the interambulacral spaces, and forming a 

 continuous depression parallel to the edge of the test. 



The ambulacral petals are broad, usually closed at the extremity ; the pos- 

 terior pair longer than the others, the anterior pair much shorter than the 

 odd petal ; the median interporiferous zone is narrow, acuminate, nearly of 

 the same width in all petals, broadest in the posterior petals; while the 

 poriferous zones are broad ; the pores large, vertically distant. The abac- 

 tinal system prominent : genital pores well marked. Seen in profile the 

 test is somewhat arched; the anterior and posterior extremity both projecting 

 beyond the level of the actinostome. The tuberculatum is moderate, com- 

 pact; on the actinal side the test is deeply scooped out; the outline of 

 the actinal surface is concave ; the ambulacral furrows are scarcely marked 

 by the absence of tuberculatum. The tubercles, which are large towards the 

 edge of the test, diminish rapidly in the median interambulacral spaces till 

 they approach the deeply sunken actinostome, when they become somewhat 

 larger again ; an irregularly tuberculated circular belt, bare in patches, is thus 

 formed at a short distance from the actinostome. The anus is usually placed 

 at a slight distance from the edge, from once to twice its diameter. Miliaries 

 closely packed cover the whole test between the primaries ; the primary 

 spines are of uniform size, shorter on the abactinal side than on the actinal 

 surface ; the longest spines immediately surrounding the actinostome are stri- 

 ated ; miliary spines very short and slender. The color of dried specimens 



