482 ME. S. O. RIDLEY ON THE GENUS DIRRHOPALTTM. 



spines ; size *19 by '003167 millim. (2) Equianchorate ; it has 

 a web connecting the two lateral teeth all but the points ; it 

 thus approaches the form called " navicular " by Mr. Carter ; it 

 measures '0158 millim. in length. Considerable numbers, grouped 

 and single, occur in the mounted specimen of the dermis. 



5. DlRRHOPALTJM MICRO CTONIDES. 



Hymeraphia microcionides, Carter, Ann. 8f Mag. N. H. (4) xviii. 

 p. 390. 



I am indebted to Mr. Carter himself for pointing out the re- 

 semblance which this species bears to the genus Dirrhojpalum. 

 Its description, together with sketches which Mr. Carter has 

 kindly furnished me, show that its structure is essentially the same 

 as that of the other incrusting species which I have referred to 

 the genus. A basal lamina contains the (1) doubly-headed cylin- 

 drical-spined spicules lying horizontally, also the equianchorate 

 flesh-spicule ; from the lamina project upwards (2) the long, 

 smooth, and (3) the small, spined, and basally contracted acuate 

 side by side. It does not appear that the smaller spined acuates 

 are grouped in whorls round the larger ones, as in D. clopetarium. 

 The colour is given as yellow, possibly owing to the presence of 

 a ceratinous uniting substance, as in other Dirrhopala. The ends 

 of the cylindrical spicule are slightly inflated, as I learn from 

 Mr. Carter, and, as stated in his description, are more abun- 

 dantly spined than the shaft. The locality is near Cape St. Vin- 

 cent, the depth 374 fathoms. It belongs to the gymnazon section 

 of the genus, but differs from the typical species, as at present 

 known, in the absence of a tricurvate flesh-spicule. 



6. DlRRHOPALUM MANAARENSE. 



Dictyocylindrus manaarensis, Carter, Ann. 8f Mag. N. H. (5) vi. p. 37, 

 pi. iv. fig. 1. 



Mr. Carter has given me all the help which he possibly could 

 with regard to its characters. An examination of mounted 

 sections and fragments of a portion of the stem of the type 

 specimen (for which I am indebted to Mr. Higgin, of the 

 Liverpool Museum) shows that, as I had been led to suspect, 

 the structure is essentially Dirrhopaline. 



Skeleton. — In the stem a very horny primary fibre (probably 

 less horny in the branches), running towards the surface, contains 

 from one to three series of stout acuates (1), the points of the 

 outermost of which project through the dermis, and it is sparingly 



