HYALJBIDjR. 



HYALJEID.S.' 



i 



elated the umbo of the . 

 tlwaye open for the ciliated 



ilwaye open fo 

 or**** 15. c 

 jJaTeadyeiit 



,'ud spperfagea. chej-ed into locomotive 

 .vs M. Deshayee, would appear sufficiently 

 j, r not. Upon UM examination of the two group* we 

 of theirdiasembUnce in all the eeaential part* of 

 To thbw. b- to mid, that it will be probably 



,iinal. [BuA<-Hu.r,-i.A] ; | Shell pyramidal, angular, very much dilated anteriorly, with a very 

 ! irge aperture, canaliciilated on each side, and rarely slit. 



M. Rang make* this sub-genus comprise (1829) five species only, two 

 of whichbe considers a* very doubtful 



C. UnetalaU. Shell compressed, elongated, lanceolate; aperture 



a IB*** 



It inhabit* the seas of warm climates. 



The following figure will convey a general idea of the form of the 



upon the 



development of the nervous 



.. . 







not a tne *yt*M, * Boeo, De Rowry, and Lamarck 

 bat . Cteodori Htmn. Rang, D'Orbigny, Leeueur and 

 I Uaimard, have principally contributed to the number of 



U the A*mi* Iridntata of Forskahl, arnelin, and 



I>illryn ; l/yalaa papilionacta of Bory de St. Vincent; //. cornea 

 of De Rolen. M. Dethaye* keep* Lamarck's synonym with a 



qo<r . Jfins.Ti/tu Idem** (I), Linnteu*. It is a native of the 



Mediterraaeaa and the tea* of warm climate*. The size scarcely 

 rsenhre that of a small hazel-nut. 



In the ' History of BritUh Mollusca,' ff. trapnota is admitted, 

 a ep+Hnvm having been taken by Mr. Robert Ball at Youghal m 

 I: 



CYm/ens. Cuvirr remark* that the dtodora, for which Brown 



orifinally founded the genus Olio, appear analogous to the Oyalaa, 

 in the simplicity of their wings and the absence of tentacles between 

 them : thru- conic or pyramidal shell, he adds, is not slit on the sides ; 

 and he quote* M. Rang'* genera and sub-genera. 



M. Detbayes, in his edition of Lamarck, states that the CUodora 

 are much more allied to the Hyal<Ht than the Clio*, approaching the 

 former not only in having a shell, but also in the form of the animal, 

 ' m a great resemblance to that of /fyalcea. It is not 



g, proceed* M. Deshayes, to see Lamarck, who had approxi- 



the Cttodora to the Clionet, indicate not very natural relations 



to the former ; for when he wrote but a very small number of species 

 were known, and he could hardly foresee that the assiduous researches 

 of Messrs. Quoy and Oaimard. Rang and D'Orbigny, should have 

 contributed to throw so much light on the Pteropods in general, and 

 the Ufolaa and Cleodont in particular. If we have before us a suffi- 

 cient number of species belonging to the two last -named genera, we 

 shall see them blend into each other so as to make it impossible to 

 draw the line between them. It is thus, continues M. Deshayes, that 

 we proceed by insensible degree* from the globular to the lanceolate 

 peon. A globular Jlyaiira seems formed of two unequal valves 

 soldered together, leaving between them a principal anterior slit, and 

 aleo lateral lita, sometimes without communication with the aperture, 

 nee forming the prolongation of this part. The posterior 

 prolonged into a spine, which is ordinarily nhort, some- 

 i straight, and sometimes curved. Taking these species of Jfyaltra 

 M the commencement of the genus, M. Deshayes points out the fol- 

 knrinjr alteration* of their characters in the rest of the series. At 

 Ant the posterior extremity is seen to be elongated, and in this case 

 UM two part* of the shell are flattened, become nearly equal, and. if 

 hi some of the specie* there remains the trace of posterior lateral slits 

 for the most pert these slit* rise sufficiently to bo in continuation of 

 the aperture. Thi* aperture is always transverse and narrow, as in 

 the /Ifalirtr properly so called. When the shells are thus eloi 

 one hare their posterior extremity curved ; others have it straight, 

 M in the CUodora. TbeM hut are elongated more and more, anil in 

 proportion * thh) elongation exists the aperture is enlarged, and the 

 lateral elite progresatvely diminish, are reduced to simple inflexions, 

 and at last entirely disappear. These change* in the form of these 

 shells are not, M. Deahaye* observe*, more extraordinary than those 

 to which be he* drawn attention in other groups, and principally in 

 the Aotpbaloos Molluak*. If, continues the same author, the animals 

 with the** modification* in their external form, their internal 

 but little alteration ; and he cites the authority of 

 Qooy and Oaimard, who assert positively that the lanceolate 

 CTmfarti diner ia nothing essentially from the Hyultrtt properly so 

 ' 1. This M. Dethaye* considers a* the more important to him, 

 inch a* be i* thereby confirmed in the opinion which he had long 

 entertained as to the analogy of the liyalaa and Clrodora. 



The following { M. Rang'* definition of CUodora : Animal of an 

 obloof or elongated form, furnished with an intermediate demicircular 

 lobe, bat baring no lateral expansions; mantle open in front; 

 braoeblst tad organ* of generation incompletely known. 



HbeD fragile, vitreous, in form of a abrath or case (game on cornet), 

 more or be* pointed posteriorly ; aperture very Urge, nearly always 

 whhoot a Jit, and without lateral a^txhwea. 



k 1 t-. i L M fa t,te, obtained many new species, 



ClnJora pyral*ii!ata. 



a, animal and shell ; t, shell, seen edgewise ; e, shell, teen from abore. 

 M. Deshayes, in his edition of Lamarck, records 13 species, beside* 

 ffyattra cvtpidata. 



2. Craii (Rang). Animal very slender ; the mantle not dilated on 

 iU sides, fins generally rather small. 



Crttit. 



a, fins ; 6, intermediate lobe ; c, mouth ; i, viscera, teen through the >hfll ; 

 X, the shell. 



Shell very Mender, fragile, and diaphanous, in the form of a straight 

 or curved cane (cornet), with nn nperture almost always as large as 

 the. shell itself, and generally without a canal; no lateral appn, 

 M. Rang, who gives this description, says, that he formed this sub- 

 genus for some very small new mollusks, which ln> frequently met 

 with in the middle of the ocean, and t<> which he unites, by analogy, 

 the genera VagituUa of Dnndin, mid the Gadut of Montagu, known 

 in the fossil state ; and M. Rang reckons 9 species. 



3. Tripter (Quoy and Uaimard). Animal oblong, fleshy, contractile, 

 furnished with two small lateral fins, and mirmoutited by a mem- 

 branous veil of the same form and size an they arc. 



Shell diaphanous, vitreous, in form of a cylindrical sheath, rounded 

 posteriorly, with a circular opening, horizontal and deutilated on ita 

 borders. 



M. Rang observes that this genus in established on a single 

 species, aud that he is inclined to believe tlint the membranon 

 decribed by Messrs. Qiioy and Oaimard is nntliim; nnnv th:m tin- 

 intermediate lolie common to all the Pteropods of the family of 

 llyaliridir, and he thinks that this sub-genus should bo united to the 

 preceding. 



Curiena (Rang). Animal elongated, furniMied with two rather 

 large fins and with an intermediate demicircular lobe; the exterior 

 branchiic situated at the ventral part, and at the base, of the inter- 

 mediate lobe ; organ of generation incompletely known; the > 

 furnished with dentiform pieces proper for mastication. 



. 



i*^ ""^| u i BHII*JB>| UUVHIUOU itrmifj uvw inHV*| 



and ctmUed their organieatwin, divide* the genus into the following 



1. CTmeVg properly so calloL Animal of an oblong form, having 

 the mantle very much dilated and advanced on each side. 



n, fln< ; I, intermediate lobe ; 



(fill* ; t, viscera, eon through 



mouth ; 

 the !irll ; /, ovaries ; f, heart ; A, shH; rf, poU'iior eavity nf the shell. 



Shell in form of a cylindrical cane, rather flattened nec.r its aperture, 

 which is heart-shaped with nharp cdge; the side opposite to the 



