25 



PLATE XI. 



POLTMASTIA BREVES, Sowerbanlc. 



Vol. ii, p. 64, ' Mon. Brit. Spongiadse.' 



Fig. 1. Represents the largest specimen of the 

 species hitherto known, from the cabinet of the Rev. 

 A. M. Norman, who obtained it at Shetland. Natural 

 size. The form of this specimen is somewhat ab- 

 normal, arising, probably, from age and accidental 

 dilapidation. 



Figs. 2, 3, 4, 5, 6. Represent specimens of about 

 the usual size, selected from among those sent to me 

 by the late Mr. Barlee, illustrating the usual amount 

 of deviations from the normal form that obtain among 

 the spongiadas. Natural size. 



Fig. 7. A longitudinal section of a specimen of the 

 normal form with an expanded base, exhibiting a view 

 of the interior of the sponge. Natural size. 



Fig. 8. A large super-fusiformi-acuate spiculuin 

 from one of the primary longitudinal fasciculi of the 

 skeleton. X 123 linear. 



Fig. 9. One of the acuate, external, defensive spicula 

 from the surface of the sponge. X 123 linear. 



By an error of the compositor and an oversight in 

 the correction of the press the spicula, in the descrip- 

 tion of the specific character of this species in p. 64, 

 vol. ii, have been designated acerate instead of acuate. 



Fig. 358, pi. xxix, vol. i, represents a small portion 

 of the side of one of the large cloacae, exhibiting the 

 structure and mode of disposition of the primary longi- 

 tudinal fasciculi of the skeleton, with a view of the 



