GASTROPOI'A 1018 



RormoUHM.) 



utili/.ed.* The tbinl >{u;iliHcation lies in the comparatively obvious fact that the 

 r.itlifr nuinerous species comprised in the genus constitute an evolutional series. 

 That this is so can scarcely escape anyone who will take the trouble to compare 

 critically the various forms which we refer here. A fourth and very important 

 quality of the genus is its convenience in classification. The use of the term 

 llnrmotoma tells us at once that we are dealing with practically imperforate shells 

 forming a high spire composed of numerous rounded or subangular whorls having 

 Mingle surface sculpture and a subcentral flat or concave band terminating in a deep 

 > shaped notch. These features furthermore are all readily apparent on all reason- 

 al-ly well preserved specimens. 



The most natural position and true relations of Hormoloma appear to be with 

 rirth'ispiru, Ulricb, on the one side, and Turritospira, Ulrich, on the other. From 

 the former it is distinguished by its higher spire, more numerous and slowly 

 enlarging volutions and deeper apertural notch; from the latter chiefly by the 

 central position of the band which, in that genus, lies considerably beneath the 

 mi. Idle of the whorls. Turritospiri may not be as closely related as the great 

 similarity of its shells leads one to suppose. Considering the position and relative 

 prominence of the band and the external contour of the whorls in that genus, 

 we see much to remind us f those low-spired and equally ancient genera 

 Euconia and Eotomaria. Accordingly we are prepared to see it proved that 

 Turritospira is nothing more nor less than a high-spired type of one or the other 

 of those genera. 



In some of its forms Lophospira slightly resembles Hormotoma, but the more 

 angular whorls and, especially, the convexity of the band in that genus renders 

 confusion in this direction highly improbable. And yet, there is a possibility that 

 some kind of relation exists between the two genera. Evidence of such a condition 

 i- furnished by two species, one, a Calciferous form described by Billings as March i- 

 >ni 'irtemtsia, the other, an Upper Silurian shell described by Lindstrom as M. 

 atttnwita Hisinger sp., which have all the characters of Hormoloma except the band 

 which is convex as in Lophospira. We are in doubt as to what should be done with 

 these geologically widely separated two species, but would advise that they be 

 referred provisionally to Hormoloma and leave it to the future to determine whether 



might br rt m~l u * subgeniu under Unrmrtum*. Setter, or poaalbly M a dUUnct 



f..r the DTonlaa rnMpofspeotes which would otherwlee Iwtor to Hnrmotomo u On- DejMsruto aetloo; prorldlng that 

 the atlt-baad In (Khlerfs type. M. (OonaasfrOf*.) baOuHtrt Ronault .p.. terminates In a abort -111. Tl.at su.-h -III 1. preeont 

 la the harMtort we Delle*e hlfhly prabaM*. aad oar Inrwtlgallons so far toad us to e* pec t Its pre-nr In th majority. :f 

 not In alt of tie DeToalaa abella agreeln otherwise t rlrtly with flmauaiii. Still, la the absence of poslUre knowledge 

 o the point, we do not conalder ourselres Justified In accepting UoHtaCrnpaa for the group of .h. 11s In question, llowerer 

 U lTrtHtlosi of Ue specie tirMlsH may tarn out. we are eoBTlaeed that less than half ..f tlir twenty spi 



to hit sabgeaos by (Ehlert really belong thre. With some of the tpecles we are Dot sufficiently acquainted to p Judg 

 meat upon them. Of the otaers we would say that it. rimgulata II Linger, and H. mmOtlamtt and Jtf . .J-lutangula of l.ind. 

 strOm. are not at preaent dUUngulahabl* from Hormntoma; that -W. mrthata UndttrOm. -V. atnntota Conrad. H. a*o*lata 

 d'Arrb. and Vrrn, and Jf. (.) raalaiaX CEhlert. belong to various sections of Loi*art*io: and that Jf. mlnla Hall, and 

 Jl. lanamt McCoy, balong to an easily reoocnlied and long II red type which we propoee to name Molma*p4ra. 



