SPONGES FROM THE WESTEEN COAST OF ?Î0RTH AMEEICA. 123 



spaces between and at a lower level than the surface ridges and covering the subdermal 

 cavities. Oscula large, often prominent, the opening sometimes measuring 3-5 mm. across ; 

 they are the outer terminations of hirge canals that traverse the interior in all directions. 

 Pores scattered, few in number, about 0-75 mm. in average diameter, piercing the dermal 

 membrane over the subdermal cavities. 



Skeleton. — Short, thick, loose strands of stylote spicules form an indefinite reticulation. 

 At the surface the dermal membrane is thickly strewn with tylota and microsclera lying in 

 it horizontally without order. The outer ends of some of the strands project beyond the 

 dermal membrane thus forming the sharp protuberances of the surface ridges. The rough- 

 ness of the surface is very probably accentuated by shrinkage in the substance of the sponge 

 due to preservation in alcohol. A considerable proportion of horny matter is present. 



Spicules. — (a) Megasdera ; of two kinds viz.: (1) Stout, slightly bent, smooth, some- 

 times slightly spined styli (Plate III., fig. 4a) ending rather abruptly in a sharp point ; 

 from 0-281 to 0-366 mm. in length and 0-016 to 0-019 mm. thick. (2) Strongyla with 

 smooth, even ends, often slightly inflated (Plate III., fig. 4b) ; from 0-222 to 0-262 mm. 

 long and about 0-008 mm. thick ; found in great abundance in the dermal membrane and 

 in small numbers in the main skeleton. 3iicrosclera ; (1) Stout, tridentate isochelœ, with 

 curved shafts and short broad teeth, (Plate III., figs. 4c, 4d) ; average length 0-052 mm. 

 Small isochelse evidently young forms of the large isochelae are abundant ; from 0-013 to 

 0-019 mm. long. (2) Sigmata (Plate III., figs. 4e, 4f ), simple and contort ; up to 0-045 

 mm. in length. The microsclera are present in large numbers in all parts of the sponge. 



Locality. — Kyska Harbour, Kyska Island (Dall), also Vancouver Island (Macoun). 



Clathria Loveni, Fristedt. 



(Plate IV., figs. 1, la.) 



Clathria Lmeni, Fristedt. 1887. Sponges from the Atlantic and Arctic Oceans and Behring Sea, (translation), 

 Vega-expeditionena vetenskapliga arbeten, p. 408, pi. 25, figs. 70-72 ; pi. 30, fig. 24. 



This species which can be readily recognized by its external form, is represented in the 

 collection by four dried specimens. The spicules are : («) Rather stout, sharply pointed 

 styli with slightly inflated basal terminations (Plate IV., fig. 1) ; from 0-383 to 0-465 mm. 

 long with an average thickness of 0-013 mm. (6) Anisochelœ (Plate IV., fig. la) with 

 an average length of 0-072 mm. Very few of the anisoehelœ were found owing to the soft 

 parts of the sponge being washed away, leaving only the firm, compact skeleton composed 

 of closely packed stylote spicules. 



The writer is inclined to regard the sponge from Cape Jakan (Siberian Arctic Ocean), 

 first described by Fristedt under the name C. Loveni, as not properly referable to the genus 

 Clathria. The typical microsclera of that genus are isochelse and the fibres are echinated by 

 small, spined styli, whereas the microsclera of the type specimen of C. Loveni and of those 

 from Alaska are anisochelœ while there is no evidence of any echination of the fibres. 



On account of these diflerences, of the general manner of growth, of the spicules of 

 which the skeleton is made up and of their arrangement, the writer considers that C. Loveni 

 is most nearly related to Esperella and would be inclined to refer it to that genus. 



Localities. — Chika Island, Akutan Pass ; Unalaska Island. 



