REPOET ON THE RADIOLAEJA. 1435 



Synopsis of the three Families and six Subfamilies of Stichocyrtida. 



Family LXVIII. \ Mouth open, .... Stichopilida. 



Podooampida. 



Three radial apophyses. J Mouth closed, .... Stichoperida. 



Family LXIX. \ Mouth open, ..... Stichophormida. 



Phormocampida. 



Numerous radial apophyses. J Mouth closed, ..... Stichophaenida. 



Family LXX. ~\ Mouth open, ..... Stichocorida. 



Lithocampida. 



No radial apophyses. , j Mouth closed, . ... Stichocapsida, 



Family LXVIII. PODOCAMPIDA, n. fam. 



Artopilida et Artoperida, Stichopilida et Stichoperida, Haeckel, 1881, Prodromus, p. 437-439. 



Definition. S tichocyrtida triradiata. (Cyrtoidea with an annulated 

 shell, divided by three or more transverse constrictions into four or more annular joints, 

 and bearing three radial apophyses). 



The family Podocampida comprises those Cyrtoideain which the lattice- 

 shell is composed of numerous (four to eight or more) annular joints, and bears three 

 external radial apophyses. It may be divided into two subfamilies, differing in the 

 shape of the terminal mouth. This is a simple wide opening in the Stichopilida (and 

 the united Artopilida), closed by a lattice-plate in the Stichoperida (and the united 

 Artoperida). The phylogenetic origin of the Podocampida may be found in the 

 Podocyrtida (p. 1314). 



Very few forms only of the Podocampida were hitherto known, viz., Stichopilium 

 (Pterocodon) davisianum, and three fossil species from Barbados, figured by Ehrenberg ; 

 Artopera loxia (united by him with Lithornithium), and two species of Pteropilium 

 (sphinx and bombus, both united by him with the three-jointed Pterocanium). In 

 general, the triradiate Stichocyrtida are much rarer and much poorer in specific forms 

 than the triradiate Tricyrtida, their ancestors. We have observed altogether only 

 forty -four species, thirty Stichopilida, and fourteen Stichoperida ; the former are dis- 

 posed among seven, the latter among three genera. 



The three radial apophyses appear either as lateral ribs or prominent wings in the 

 thorax (PI. 77, fig. 812), or as three terminal feet around the mouth (PI. 97, fig. 15). 

 Sometimes the ribs are replaced by three radial combs, or rows of spines, and these may 

 be united by three divergent beams, forming three vaulted bridges with numerous 

 bows (PL 75, figs. 10, 11). The lateral wings or ribs, as well as the terminal feet, are 

 either solid or fenestrated. 



