REVISION OF PALEOZOIC STELLEROIDEA. 251 



and both dorsally and ventrally have the structure of Encrinaster. 

 The adambulacrals are also opposite to the ambulacrals, and have 

 long forward directed spines. In regard to the dorsal position of 

 the madreporite, he states that the abactinal area has been mistaken 

 for the actinal, and that therefore the madreporite lies upon the 

 ventral side. 



The disk is not circular in outline, but concave between the inter- 

 radii. 



LAPWORTHURA MILTONI (Salter). 



Protaster miltoni SALTER, Ann. Mag. Nat. Hist., ser. 2, vol. 20, 1857, p. 330, pi. 9, 

 fig. 4. WRIGHT, Mon. British Foss. Echinod., Oolitic, vol. 2, pt. 1 (Palse- 

 ontogr. Soc. for 1861), 1862, p. 32, fig. 18. QUENSTEDT, Petrefactenkunde 

 Deutschlands, vol. 4, 1876, p. 75, pi. 92, fig. 36. STURTZ, N. Jahrb. fur Min., 

 etc., 1886, vol. 2, p. 148; Palseontographica, vol. 32, 1886, pp. 79, 94, pi. 8, 

 fig. 6. 



Lapworthura miltoni GREGORY, Proc. Zool. Soc. London for 1896, 1897, p. 1037, 

 fig. 5. SCHONDORF, Palseontographica, vol. 57, 1910, p. 58; Jahrb. nassau- 

 isch. Ver. Naturk., Wiesbaden, vol. 63, 1910, p. 208. SOLLAS and SOLLAS, 

 Philos. Trans. Roy. Soc. London, ser. B, vol. 202, 1912, p. 214, text figs. 1, 

 2, 4 D, pi. 9, figs. 1, 2; pi. 10, figs. 1-4. SPENCER, Mon. Brit. Pal. Aster- 

 ozoa, pt. 1 (Palseontogr. Soc. for 1913), 1914, pp. 25, 32, 35, 36, pi. 1, fig. 9. 



Formation and locality.- Abundant in the Lower Ludlow of the 

 Siluric at Leintwardine, England. See elsewhere in this work 

 (p. 237) under Sturtzura leptosoma, which Schondorf states is but 

 the young of L. miltoni. The same author states further that the 

 latter species either embraces several species or the form has a long 

 geologic range, for a number of species and genera appear to be 

 identical with L. miltoni. . 



Cat. No. 59394, U.S.N.M. 



LAPWORTHURA SOLLASI Spencer. 



Lapworthura sollasi SPENCER, Mon. Brit. Pal. Asterozoa, pt. 1 (Palseontogr. Soc. 

 for 1913), 1914, pi. 1, fig. 10. 



Occurs in the Siluric of Great Britain. 



LAPWORTHURA (? "probably n. gen.") species (Miller and Gurley). 



Aganaster (?) sp., MILLER and GURLEY, Sixteenth Rep. Geol. Surv. Indiana, 

 1891, p. 372, pi. 9, figs. 12, 13; authors' extracts, 1890, p. 58. GREGORY, 

 Proc. Zool. Soc. London for 1896, 1897, p. 1038. ' 



Original description. "We have figured this fragment to show the 

 anchylosis of the oral plates, and the pores passing through the 

 ambulacral plates, and also those passing between them. It will 

 be observed that one pore passes through each plate near the marginal 

 end, while a double row of pores passes between the plates in the 

 central part of the arm furrow. We believe this is an Aganaster, 

 from the <Jepth of the central part of the disk, and the arrangement 

 of the plates in the arm furrows; but the specimen is larger than any 



