NORTH AMERICAN INVERTEBRATE PALEONTOLOGY. 567 



SO far as relates to the palseozoic forms. In that notice the reasons for 

 the generic subdivisions used in the present vohiiue will be given in full. 



The following new genera are proposed in this volume :. Grenipecten, 

 Lyriop€cten, Fterinopecten, Actinopteria, Ptycliopteria, Limoptera, Gh/p- 

 todesma, Leiopteria, Leptodesma, Palceopinna, Uctenodesma, Byssopterla, 

 and three subgenera, Plethomytilus a s. g. of Mytilarca Hall, Mytilops a 

 s. g. of Modiola, and Vertumnia a s. g. of Pterinea. All these are re- 

 published, except Vertumnia, with but few modifications from the few 

 pages of text preceding the volume of plates published the year previous. 



The following new species are described: Aviculopecten cequilateralis, 

 Pterinopecten reflexus, P. nodosus, P. Iwtus, P. intermedius, P. regularis, 

 P. dispandus, Pterinea grandis, Pterinea inter strialis, P. {Vertumnia) 

 reproha, Actinopteria doris, A. pusilla, A. tenuistriata, A. auriculata, A. 

 eta, A. theta, A. iota, A. Jcappa, PtycJioptteria thetis, P.falcata,P.spio, P. 

 eudora, P. trigonalis, P. elongata, P. galene, P. beecheri, P. spatulata, P. 

 lata, P. perlata, P. thalia, P. gibbosa, P. lobata, P. 'vanuxemi, Leiopteira 

 sayi, L. troosti, L. leai, L. gabbi, L. linguiformis, L. torreyv, Leptodesma 

 shumardi, Leptodesma agassizi, L. billingsi, L. stepliani, L. medon, L. cad 

 mus, L. creon, L. demus, L. loxias, L. mentor, L. hector, L. clitus, L. trun 

 catum, L. corydon, L. jason, L. pelops, L. orcus, L. nereus, L. alatuvi, L 

 orus, L. biton, L. lesleyi, L. aviforme, L. flaccidmn, L. patulum, L. arci 

 forme, L. pliaon, L. propinqimm, L. quadratum, L. acutirostrum, Ptero 

 nites inoptatus, Mytilarca (Plethomytilus) Jcnappi, Mytilarca regularis, M 

 gibbosa. 



Hambach, G. — iS'otes about the Structure and Classincation of the Pen- 

 tremites. (Trans. Acad. Sci. Saint Louis, vol. iv, No. 3, pp. 537-547. 

 Saint Louis, 1884.) 



A portion of the paper is devoted to answering Mr. Carpenter's criti- 

 cisms on the author's paper on .the Anatomy of the Bhistoidea. The 

 author considers Penlremites more closely related to Echinus than to 

 the Crinoidea; he considers it impracticable to divide the genus Pen- 

 tremites into four or five new genera, as has been proposed by Mr. Carpen- 

 ter. Mr. Hambach thinks that all described Pentremites (except those 

 which belong to the genus Codaster orCodouites) can easil}^ be distributed 

 in one of these three divisions, viz: First division comprises all species 

 in which the horizontal i^ortion of the deltoid piece is very narrow, the 

 sinus to both sides in the deltoid and lancet pieces comi)aratively large, 

 and so snrrounded bj" the zigzag plicated integument that two* of the 

 80 formed openings appear externally only as one, e. g., P. florealis 

 Say, and P. reimcardtii Troost. The second division comprises all 

 species in which the deltoid pieces are very broad, the lancet pieces 

 very narrow, and the sinus for the formation of the spiracle openings 

 in both deltoid and lancet i^ieces very little ; the zigzag plicated in- 

 tegument corresponding to the narrow ambulacra! field is not wide 

 enough to surround these openings fully, hence they have to remain 



