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Isometra vivipara Mortensen; development described^ the present author, 

 1920. 



Compsometra serrata (A. H. Clark); part of the development described, 

 the present author, 1920. 



Tropiometra carinata (Lamarck); reared through metamorphosis, the pre- 

 sent author (1916), 1920. 



Notocrinus virilis Mortensen; larva described, the present author, 1920. 



In the present memoir are given, besides additional observations on 

 the development of the following species : Strongylocentrotus franciscanus, 

 Lytechinus variegatus, Tripneustes esculentus and Peronella Lesueuri, obser- 

 vations on the development and the larval form of the following species, 

 which were hitherto entirely unknown as regards their development: 

 Phgllacanthus parvispinus Woods; cleavage and gastrulation only. 

 Eucidaris Thouarsi (Val.); reared to beginning pluteus. 

 Arbacia stellata (Blv.); pelagic larva identified. 

 Diadema antillarum Phil.; reared to first larval stage. 

 Astropyga pulvinata (Lamk.); reared to first larval stage; pelagic larva 



identified. 

 Tripneustes gratilla (Linn.); reared to first larval stage. 

 Lytechinus anamesus H. L. Clark; reared to full larval shape. 

 Lytechinus pictus (Verrill); reared to first larval stage; fully formed pelagic 



larva identified. 

 Lytechinus panamensis Mrtsn. ; reared to first larval stage. 

 Lytechinus verruculatus (Ltk.); reared to first larval stage. 

 Toxopneustes pileolus (Lamk.); reared to first larval stage. 

 Toxopneustes roseus (A. Ag.); reared to first larval stage; pelagic larva 



of more advanced stage identified (not beyond doubt). 

 Pseudocentrotus depressus; reared to first larval stage. 

 Strongylocentrotus pulcherrimus (A. Ag.); reared to nearly full larval shape. 

 Temnopleurus toreumaticus (Klein); reared to nearly full larval shape. 

 Temnotrema sculpta A. Ag. ; reared to nearly full larval shape. 

 Mespilia globulus (Linn.); reared to full larval shape. 

 Evechinus chloroticus (Val.); reared to full larval shape. 

 Heliocidaris tuberculatus (Lamk.); reared to full larval shape. 

 Heliocidaris erythrogramma (Val.); reared through metamorphosis. 

 Echinometra lucunter (Linn.); reared through metamorphosis. 

 Echinometra oblonga (Blv.); reared to nearly full larval shape. 

 Echinometra Mathsei (Blv.); reared to first larval stage. 

 Echinometra van Brunti A. Ag.; reared to first larval stage. 

 Colobocentrotus atratus (Linn.); reared to nearly full larval shape. 



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