128 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



i 



8J 







I 



Owing to the contractions incident to preservation the neck or con- 

 stricted part of the body was found broken in nearly every specimen. 

 Length of the largest zooids when removed from the test in their 

 partly contracted condition 30 to 35 mm. The thorax when ex- 

 panded forms considerably over half the length, but in the contracted 

 state only about one-half or less. Branchial aperture plain or only 

 obscurely lobed; atrial aperture prominent, anteriorly directed and 

 provided with 6 distinct lobes. 



Mantle thin, provided with a very variable number of conspicuous 



muscle bands which on the sides of 

 the thorax are rather irregularly 

 distributed and longitudinal in di- 

 rection, but curve and assume a 

 transverse direction at their pos- 

 terior ends, so that they approach 

 either the endostyle or the median 

 dorsal line. At the same time they 

 divide or spread out into a number 

 of narrow bands. 



Other transverse muscles (except 

 about the apertures) are few and 

 weak. No conspicuous muscle 

 bands on the abdomen. 



In one specimen seven large ten- 

 tacles were counted, additional 

 smaller ones of at least two orders 

 are somewhat irregularly distrib- 

 uted in the intervals. Small pa- 

 pilla-like prominences farther for- 

 ward within the branchial tube 

 may represent rudimentary tentacles of higher orders. 



Dorsal tubercle large, elongate oval, with an elongate oval orifice. 

 Dorsal lamina represented by a series of triangular languets ex- 

 panded in a direction transverse to the median dorsal vessel from 

 which they arise. 



Branchial sac with numerous (sometimes 100) transverse vessels 

 which are of nearly uniform size and bear attached along their length 

 a membrane raised into triangular supporting papilla? that carry 

 slender internal longitudinal vessels. These are attached almost but 

 not quite at the tips of the supporting papillae (that is, the latter 

 project a very little above the internal longitudinal vessels). In 

 some places the latter vessels are incomplete and interrupted, so that 

 they appear only as short lateral branches of the supporting papillae, 



84 



Figs. S2-S4. — R iiopalopsis crassa 

 (IIerdmax). 82, Outline of zooid 

 (removed from test) showing course 

 OF MUSCLE bands on mantle and out- 

 line of intestinal loop. X 2. S3, 

 Dorsal tubercle and part of dorsal 

 lamina. X 20. 84, Part of branch- 

 ial sac. X 20. 



