68 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



• 



has not seemed necessary to give family and generic diagnoses in the 

 present paper. For these the reader is referred to the above work of 

 Hartmeyer. Any material deviations from his system are explained. 



In giving the number of internal longitudinal vessels in the 

 branchial sac of simple ascidians the total number, including those 

 on both sides of the folds, has been given, not the number on the 

 exposed side only, as some writers have done. 



The illustrations are from photographs and drawings by the 

 writer. The drawings have been made more or less diagrammatic. 



Abbreviations used in the text figures. 



at, atrial aperture. 



br, branchial aperture. 



c, caecum. 



fp, faecal pellet. 



g, gonad. 



t, intestine. 



inc, incubatory pouch. 



7c, kidney. 



I, liver. 



mp, muscular process. 



od, oviduct. 



r, rectum. 



sd, sperm duct. 



st, stomach. 



Family MOLGULIDAE Lacaze-Duthiers, 1877. 



[=CAESIRIDAE Hartmeyer, 190S.] 



Genus MOLGULA Forbes and Hanley 1848. OCAESIRA Fleming, 1822.] 



MOLGULA VITREA Sluiter, 1904. 



1904. Molgula vitrea Sluiter, Tunicateu der /Sibotfa-Expedition, pt. 1. p. 



119, pi. 14, figs. 17-19. 

 1909. Caesira vitrea Hartmeyer, Bronn's Tier-reich, vol. 3, suppl., p. 1324 



Body oval, somewhat compressed laterally, anchored or lightly 

 attached at the smaller end by a tuft of rootlike hairs; apertures at 

 or near the opposite (or free) end, the branchial only moderately 

 prominent in the contracted specimens, the atrial on a rather large 

 tube of moderate length. The apertures are well separated, the 

 branchial with 6, the atrial with 4 small pointed lobes. Test only 

 moderately thick, transparent, gelatinous and colorless in formalin 

 specimens, its surface much wrinkled and sparingly and unevenly 

 covered with short stout crooked somewhat branched hairs to which 

 mud adheres. A greater development of these hairs on the ventral 

 region forms the tuft already mentioned by which the animal is 

 attached. In the soft collapsed condition of the specimens accurate 

 measurements are impossible. Size of largest individual about 

 20 mm. by 12 mm. 



Mantle musculature of characteristic and conspicuous typej consist- 

 ing of broad rather crooked bands, longitudinal and transverse ones 

 predominating, but these anastomose, branch, and are accompanied 

 by so many oblique and irregular ones that a conspicuous network 

 with coarse squarish or oval meshes is formed. 



