NORTH AMERICAN INVERTEBRATE PA li^ONTOLOGY. 567 



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

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



The following new genera are proposed in this volume: Crenipecten, 

 Lyriopecten, Pterinopecten, Actinopteria, Ptychopteria, Limoptera, Glyp- 

 todesma, Leiopteria, Leptodesma, Palceopitma, Eclenodesmn, Byssopteria, 

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

 s. g. of Modiola, and Vertunmia 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 j)revious. 



The following new species are described: Avicnlopecten cequilateralis, 

 Pterinopecten refiexus, P. nodosus, P. Icetus, P. intermedius, P. regnlaris, 

 P. dispandus, Pterinea grandis, Pterinea interstrialis, P. [Vertumnia) 

 reproha, Actinopteria doris, A. pnsilla, A. tenuistriata, A. auriculata^ A. 

 eta, A. theta, A. iota, A. Icappa, Ptycliopteria tlietis, 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, Leiojjteira 

 sayi, L. troosti, L. leai,_ L: gabbi, L. linguiformis, L. torreyi, Leptodesma 

 shumardi, Leptodesma agassizi, L. billingsi, L. stephani, L. medon, L. cad- 

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

 caium, L. corydon, L. jason, L. pelops, L. orcus, L. nereus, L. alatum, L. 

 orus, L. biton, L. lesleyi, L. aviforme, L. flaccidum, L. patulum, L. arci- 

 forme, L. pliaon, L. propinquum, L. quadratiim, L. acutirostrum, Ptero- 

 nites inoptatus, Mytilarca {PletJiomytilus) hnappi, Mytilarca regularis, M, 

 gibbosa. 



Hambach, G. — ]!^otes about the Structure and Classification 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 Blastoidea. The 

 author considers Pentremites more closely related to Echinus than to 

 the Crinoidea; he ponsiders it impracticable to divide the geuus 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 CodasterorCodonites) can easily be distributed 

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

 in which the horizontal portion of the deltoid piece is very narrow, the 

 sinus to both sides in the deltoid and lancet pieces comparatively large, 

 and so surrounded by the zigzag plicated integument that two of the 

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

 Saj^, and P. reinwardtii Troost. The second division comprises all 

 species in which the deltoid pieces are very broad, the lancet i)ieces 

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

 in both deltoid and lancet pieces 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 



