PLATE VI. 



Fig. i. Group of eight spicules of Peltastisis cornuta Nutting, a, one of the opercular spicules; b, one of 

 the spindles of the ccenenchyma; g, a spicule intermediate between the calyx scales and the 

 spindles of the ccenenchyma; c, d, e, f, i, scales from the calyx walls. All x 120. 



Fig. 2. One of the "bony stays" consisting of a single peculiar spicule of Peltastisis cornuta Nutting X 64. 



Fig. 3. Group of five spicules from Peltastisis uniserialis Nutting X 120. e, one of the characteristic trian- 

 gular spicules of the operculum; a, b, c, spindles from the ccenenchyma; d, calyx scale. 



Fig. 4. Group of six spicules, a, b, c, d, e, f, from Mopsea alba Nutting X 120. 



Fig. 5. Calyx of Peltastisis cornuta Nutting X 64. op., opercular scale; s. curious "bony stay" which is 

 formed of a single very large spicule and supports the calyx in front. 



