444 University of California Puhlimtions in Zoology [Vol. 16 



Intestine on left side; stomach wall not folded, intestine divided into several 

 distinct sections. 



Sexual organs on left side in the intestinal loop, ovary a single mass, testes 

 in numerous lobes. 



Budding stolonic. 



Genus 12. Distaplia (Holozoa, some authors) 



Colony usually consisting of short club-shaped or capitate masses closely 

 united at base; zooids typically in systems with distinct common atrial orifices; 

 cellulose mass soft, usually highly colored. 



Form of zooids: body elongated, separated into thorax containing branchial 

 sac, and abdomen containing intestine and sexual organs; branchial orifice 

 6-lobed, atrial with a long dorsal tongue, or languet. 



Branchial sac with neither folds nor internal vessels, four series of stigmata. 



Intestine a simple, elongated loop; stomach ovate, wall not folded but with 

 a network of fine ridges on inner surface. 



Sexual organs: gonads situated on the right-posterior part of the intestinal 

 loop, ovary very simple, ripe ova large; testis composed of a few masses; 

 larvae develop in an incubating pouch. 



Budding stolonic. 



Genus 13. Eudistoma 



Colony massive and variously lobed; dull white or dark from covering of 

 sand; zooids not usually grouped in systems. 



Form of zooids: body elongated, divided into thorax and abdomen; a long 

 ectodermal process usually given off from posterior end of abdomen; orifices 

 each 6-lobed. 



Branchial sac simple with few (three to five) series of stigmata. 



Intestine a long, nearly straight, simple loop; stomach smooth-walled, fre- 

 quently far back in the abdomen. 



Sexual organs: gonads alongside the intestinal loop, far back; ovary simple; 

 testis of numerous lobes; no incubating pouch. 



Genus 14. Dldenmum 



Colony always closely encrusting, usually very thin, rarely somewhat mas- 

 sive; cellulose material containing stellate calcareous spicules; zooids not in 

 systems; color white or variously tinted. 



Form of zooid: divided into thorax and abdomen; branchial orifice 6-lobed, 

 atrial orifice plane, situated on dorsal side of thorax. 



Branchial sac with four rows of stigmata. 



Intestine a simple loop, its posterior part usually containing the stomach; 

 stomach smooth-walled. 



Sexual organs situated on the left-posterior side of the intestinal loop; ovary 

 very simple, ripe ova very large; vas deferens wound in a close spiral around 

 the testis. 



Genus 15. Trididemnum 



Scarcely differing from Didemnum except in the number of stigmatic series, 

 these being here three; colony perhaps typically somewhat more fleshy. 



Genus 16. Diplosoma 



Colony mostly thin and encrusting, soft and lax because of numerous great 

 spaces in the transparent cellulose mass; systems where present very irregular. 



Form of zooids: divided into thorax and abdomen; not sharply separated 

 from each other; branchial orifice 6-lobed, atrial a large, simple opening. 



Branchial sac with four rows of stigmata. 



