PLATE XXXIX. 
Figs. 1-10. — Idia pristis (p. 85). 
Fig. 1. — A colony ; natural size. 
Fig. 2. — Part of a pinna, superficial view from the front ; magnified 15 diameters. 
Fig. 3. — The same, posterior aspect, focussed at some distance from the surface, showing 
the polygonal areas into which the common cavity is divided by offsets of 
the perisarc ; magnified 1 5 diameters. 
Fig. 4. — The same ; optical longitudinal section, deeper than that of fig. 3, showing the 
anterior chambers with their coenosarcal lining ; magnified 1 5 diameters. 
Fig. 5. — Lateral view; longitudinal section showing the common posterior chamber 
and two of the anterior chambers with their corresponding hydrothecse, in 
which the bases of the hydranths are still preserved ; magnified 25 diameters. 
Fig. 6. — One of the internodes of the main stem, showing the reticulated condition of its 
coenosarcal lining ; magnified about 1 5 diameters. 
Fig. 7. — Portion of main stem with gonangia ; magnified about 12 diameters. 
Fig. 8. — Transverse section through a pinna ; magnified 25 diameters. 
a. Basal part* of hydrotheca. 
b. Anterior chamber. 
c. Common posterior chamber. 
Fig. 9. — Outline of distal extremity of hydrotheca, showing its valvular orifice. 
Fig 10. — Origin of a pseudo-branch ; slightly magnified. 
