ECHINODERMA TA—ECHINOIDEA . 



60 1 



XXXII. LiNTHiA Merian. 

 Test heart-shaped, longer than broad; anterolateral ambulacra 

 differing from the posterolateral in shape and construction. An- 

 terior ambulacrum in a deep groove, the pores round and small, in 



Fig. 1935. Hemiaster lacunosus. «:, apical system, greatly enlarged (^, genital 

 plates ; m, madreporite ; r, radial plates) ; b^ portion of anterior petal where it joins 

 the apical system, greatly enlarged ; c, several plates of the right anterior petal, greatly 

 enlarged. (After A. W, Slocum.) 



pairs on either side. Anterolateral ambulacra longer and more 

 divergent than the others, with petals sunk in grooves. Pores 

 united by grooves. A peripetalous and lateral fasciole present. 

 Cretacic-Recent. 



49. L. variabilis Slocum. (Figs. 1911, 1936.) Cretacic. 



About half the size of L. tumidula, the posterior portion often 





Fig. ^936. Linthia variabilis, several plates of the left posterior petal, greatly 

 enlarged ; apical system, greatly enlarged; several plates of the anterior petal, greatly 

 enlarged. (After A. W. Slocum. ) 



strongly elevated and truncate; ambulacral petals proportionately 

 shorter and broader. 



Ripleyan of Mississippi. 

 50. L. tumidula Clark. (Fig. 1937, a-J.) Cretacic. 



Test elevated. Apex central. Posterior border obliquely trun- 

 cated, bearing the anal opening. Fascioles distinct. 



Jerseyan (Vincentown lime sand) of New Jersey. 



