346 SIR SIDNEY F. HARMER ON 
retaining the characteristic position of the joint at the bifurcation. This^ 
sjDecies has a close resemblance to M. spicata in all essential details of 
structure ; and its internal avicularia (figs. 29, 30) found also in other 
species (see Sect. III.) are a striking point of agreement. Another resem- 
blance is the occurrence in both species of calcareous spines projecting into 
the body-cavity, as originally described by Levinsen. On separating the 
two laminae of a branch of Ai. rohorata, after boiling in Eau de Javelle, it is 
found that while rosette-plates are wanting in all the zocecia of the median 
rows, typical lateral rosette-plates occur on all those of the two marginal 
rows. M. ligulata shows a distinct tendency to curve the margins of its 
branches towards the basal surface. If this process were continued until 
the edges united to form a hollow unilaminar cylinder, with the basal 
surface internal and the frontal surface external, and if this cylinder were 
then compressed so that the cavity disappeared and the basal walls of opposite 
sides came into contact, a bilaminar branch would result. At each lateral 
margin the external zooecia would be united by rosette-plates, while noue of 
the others would be thus united. This is the arrangement actually found in 
M. rohorata. 
Specimens (slides) in the British Museum : 97.5.1.45.5, 457, Victoria, 
Bracebridge Wilson Collection ; 81.10.21.352-354, Port Jackson ; 50.5.2.2. 
12. Menipea vbctifera*, n. sp. (PI. 17. fig. 23; PL 18. figs. 36-39.) 
Unilaminar, the frontal surface flat, the basal surface also flat or slightly 
convex ; the branches composed of as many as seven series of zooecia, and 
bordered by lateral bundles of rootlets. Apparently not normally jointed,, 
although secondary breaks are formed across the branches, becoming 
converted into joints by the development of irregular chitinous tubes. 
Habit as in M. spicata, but less calcified. Cryptocyst (fig. 23) finely tuber- 
cular, the proximal part extensive, especially in the marginal zooecia, the 
free edge narrow on the distal side of an ovicell. A pair of long bars, ' 
expanding at their free ends in a palmate manner (figs 37, 39), descend 
from the thickened edge of the proximal cryptocyst into the body-cavity, 
their direction being nearly vertical, but with a slight slope proximally. 
Spines small, 2, 2, the inner or distal pair commonly vestigial and recognizable 
by their tubular cavities trasversing the oral frame, as seen in a Canada 
balsam preparation. Frontal avicularium single, asymmetrical, commencing 
at one edge of the proximal cryptocyst, the rostrum directed transversely or 
slightly proximally, the mandible rather elongated and linear distall3\ On 
the distal side of an ovicell two frontal avicularia occur, widelj' separated, 
their rostra reversed so as to point distally and outwards. Internal 
avicularia (fig. 36) found in several cases in the more proximal zooecium of 
the two formed when a row is doubled, close to the concave side of the^ 
* Vectis, a bar ; referriDg to the t-wo bars borne by tbe proximal cryptocyst. 
