2/G CONTRTr.U^'IONS FROM TJIK NATIONAT. HF.RIVVinUM. 



Asteromphalus nanus Mann. pp. nov. Plai'k XLV, fiouhk 4. 



Valv(^s circular, th(^ ccndal liyaline aroa or rosottc^ inu.'(pially divided inio Jivo 

 wedgo-shapod pogmcnts l>y .straight or ylighUy c urvcd partiLion.s, luiving neitlun- forks 

 nor angular l)rc>aks, tlicfoi-uri of the livc' scgnicnl.s being not in llu^ ccuLcr of ihv valvf, 

 Lul .slightly noarrr Iho side bearing tlic narrow liiid); tho wcdgt^-shapod scguicnl of 

 the narrow lind> smallest, conslilnling about ]2 per cent of tlu^ cenlnd area, the two 

 on either ^ido larger, each about 20 percent of the area and the reniaininfr two lanrest, 

 about 24 per cent ; narrow limb sharply bi'Ut to the left, dividing the Ix^aded com- 

 part nuMits on either sitle of it into tw^o une([ual portions; of the four rcMualning hudxs 

 one or Uvo >':^lighily curved; all four ^^tout, expand(Hl at the ends and bearing a minute 

 circular procet^s at the extremity; all five llndjs rt^aching to within one row uf biiuling 

 of the margin; beading fine, decreasing toward (lie margin: 0])pnjximately n^gular, 

 the flight deviation from r(^gularity being re[)ealed (^xaclly in each of th<^ pair^ of 

 eompartnienlg to the light, and left of the narrow limb. The sp(H'i(^s is very abundant 

 in the one .-ouuding wIktc it was <liscover(\l and is constant to ils type, 



Diain(^t(^r of valve 0.04 to 0.0(i mm.; rows ot beacUng 13 to 15 in 0.1 mm. 



Type in the U, S. Naticmal Museum, Xo. 590128, from .^tatidn 102011, Bering Sea, 

 June 27, 1900; 913 fathoms, bottom of gray sautl and clay. 



The nearest form 1o this is .1. dchi/l Pant.^ It diTfers from the lulU^r in the character 

 of the heading and in the al>senc(.^ of iseptae joining the dividing lines of the w^edge- 

 nliaped si'guients of the t-entral rosette. 



Asteromphalus roperianus (Grev,) Ralfs. in Pritch. ITisl. Tnfus. ed. 4. 838. bSlJl. 



Schmidt, Atlas pi 3S.f. 15. 1870. Ratt. Proc, Roy. Soc. IvHnb. 16: (i57. 18S9. 



Castr. Rep. Voy. Chall. Mot. 2: 133. pi 5.f. 3. ]88()'. Schultz.s Hull. Torr. Club 



14: 90. 1887. I3e Toni, Syll. Alg. 2: 1111. 1894. 

 Asterolaui pra roperiana Crev. Trans. Micr. Sue. Loud. n. s. 8: 119. pi 4,/^ /,;. JSGO. 



Moel). Diat.-taf. pi 33, f. I4. 1890. 

 Mesastcrias ahyssi Ehr(id). Phys. Abh. Akad. WisH. Berl. 1872: 392. 7^/. .9./. 



1873. 

 Found at station 2807, Galapagos Islands. 



Asteromphalus shadboltianus (Grt^v.) Ralfs in Pritch. IIi.4. Infus. ed. 4. 838. ISOl, 

 Schmidt, Atlas pl38.f.J7.iS:rr^plJ37,f,26.1&Sd. Ratt. Pruc. Roy. Soc. 

 Edinb. 16: G5G. 1889. DeToni, Syll. Alg. 2: 1111. 1894. 



Aslcrolatitpra shadboUlana Grev. Trans. Micr. S(jc. Lend. n. s. 8: 121. pi 4./. v,K 

 18(;0. Moeb. Diat.-taf. pi 33. f. 19. 1800. 



Found ^t stations 2919, 2920II, :;(]88II, near Hawaiian Islands and in Okhotsk Sea. 



Asteromphalus van heurckii Mann, sp. nov. Pi..\tk XLV, p^igiju-: Tj. 



Valve circular, scarcely conv<^x, extremely delicate an<l translucent; radiatin^^ 





limbs 12; central hyaline area or rosette laigc, divided somewhat unequally into 12 

 wedge-shaped segments by tortuous partitions, the segment belonging to the narrow 

 liml^ alone reaching the center of the valve and narrower than tlie rest; limbs straight, 

 slenchT, terminating at tlu* margin of the valve in sudd( nly enlarged extremities, 

 bearing a minute process; margin narrow but 1 vith iilly striated; markings of tlu' 12 

 external wetlg<'-shaped compartments very delicate, appearing under magnilicatiuna 

 of 200 to 250 diameters to cc^nsist i)i delicate parallel lines conccmtric with the periphery 

 of the valv(\ but under the higlu^sL magnihcatitm resolved into line iniuiiliform striae, 

 those nt^aresL the periphery alone parallel lo it, tliose nearer the cent(T becomint^ 

 curved in the opposite direction — that is. with the convexity inward — the striae 

 slightly wider apart than the width of the l)eading; the beading next to the limbs 

 separating th<' compartments and berdering the internal conv<^x ends of the com- 

 partments double the size of the rt^st of the beading, forming a single row of large 



t^iieilr. RacilL Ung. 3: pi 21. f. 305. 1893. 



