482 Universitij of California Publications in Zoology [Vol.16 



species is most akio. According to this revised definition, tlie only 

 difficulty in the waj' of this disposition of the species is the break- 

 ing-up of the colony of both 2M>'-f>'stis and pelluciduni into club- 

 shaped masses. In view, however, of what occurs in the various other 

 allied genera, this difficulty can hardly be regarded as serious. What 

 may be of more importance as touching the integrity of Macroclinum 

 is the discovery by Van Name (1910) that the inner surface of the 

 stomach of M. pomum (S.\r), which should be the type species of the 

 genus, is areolated. This fact raises the question of whether further 

 study may not make it advisable to retain the genus Aplidiopsis 

 hah., which Hartmeyer has assumed to be synonymous with Macro- 

 clinum, for the smooth-stomached species. Should this turn out to 

 be so. par-fustis and pellucidum would be transferred to Aplidiopsis, 

 for there is no trace of areolation in the stomachs here. 



Macroclinum pellucidum, n. sp. 



PI. ::!9, fig. 9; pi. 45, fig. 62 



Superficial characteristics of the colony. — Pyriform with peduncle 

 as long as and often longer than globular portion ; entire length about 

 1.5 cm. Anterior surface somewhat flattened with one large, centrally 

 located, common atrial orifice; around this usually three to six 

 branchial orifices; branchial orifices 6-lobed ; common atrial orifice 

 indistinctly 12-lobed. Colony colorless and tran.sparent, making 

 zooids distinctly visible through test ; test tough on outer surface and 

 only thin partitions between zooids within (pi. 39, fig. 9). 



Zooids. — Occupying greater part of globular portion of colony, 

 though unusually contracted in preserved specimens. Branchial sacs 

 often broken loose at orifice and forced out through opening by 

 shrinkage of colony. Thorax, abdomen, and postabdomen each about 

 3 mm. long. Mantle with about twelve wide, longitudinal muscle bands 

 on a side, the.se separated by spaces several times wider than bands; 

 band.s running together ju.st below branchial sac ; lodged in a depres- 

 sion on ventral side of zooid between arms of intestinal loop, and con- 

 tinuing posteriorly into peduncle, where they disappear in a large 

 lobe of granular material, probablv accumulated food (m.b., f.m., 

 pi. 45, fig. 62). 



Branchial system. — Branchial siphon indistinctly 6-lobed; atrial 

 with flat, truncated languet having usually three or four lobes. 

 Branchial sac with eleven series of long, narrow stigmata, about 

 twenty in half-series; most posterior series having longer stigmata 

 than others; stigmata of last series gradually shorter toward endo- 

 style; in younger zooids number of series less than eleven, .stigmata 

 at the ends of a half-series small, oval, gradually becoming longer 

 toward middle of series. Dorsal languets long and flat, with broad 

 flat bases which merge into membrane of transverse vessels upon whicli 



