OjG GEOMALACUS MACIU.OSUS. 



The LiN'i;uAL memukane is about eight mill, long and two mill, wide, and is 

 siiiil liy Heyiieiiiann Id be com)iosfd of 240 slightly curved tvan«ver.se rows of 

 denticles, each row composed of a median tooth and lifty-seven lateral and marginal 

 teetli at each side. T'he mwlian teeth are small and clearly unicuspid, tliough 

 slightly sliouldered ; tlie lateral teeth are all liicuspiil, but the admedian teeth are 

 noticeably larger tlian the median row, and the nie.socoue is M'ell developed, there is, 

 however,' no distinction between the lateral and marginal .series except that the 

 ectocone present on the admedian teeth recedes in position ami slightly diminishes 

 in size in the succeeding teeth up to about the twentieth row, but in the marginal 

 series the ectocone gradually grows in si/e and importance as the margin is 

 approaclied, wliile the meso'cone becomes almost correspondingly diminished, the 

 outermost teeth showing a more embryonic character; judged by the theory of 

 nieso-metamoiphosis the tendency of tlie teeth development is towards an uni- 

 cnspidate dentition. 



30 40 45 50 J, 52 5* 



Fig. 269. — Representative denticles from a transverse row of the teeth o{ Geomatacus /iiacu/osus, from 

 Lough Caragh, Ireland ; from a preparation by Rev. Prof. H. M. Gwatkin. 



The formula of a Lough Caragh specimen is, according to Heynemann : 



jyi + ;^T + 1 + 2^' + Y- X 240 = 27,600. 



Reproduction and Development.— The congres.s of this species has 

 not been observed or described, but judging by its structure, it is, accord- 

 ing to Simrotli, - i 

 probably similar 

 to that of L'nmix 

 maximum, the long 

 ])rotruding penes 

 intertwining spir- 

 ally together dur- 

 ing the process, 

 as in the latter 

 species. The sper- 

 matozoids must 



possess a very ' .' . .i-'i^Sf'., 



persistent vitality 



or the -aminai be Fig. 270.— cluster of eggs of G(r£7/«a/acz(j-;«<ic«/£'jwj, deposited in captivity 



capable of auto- (photo, by Mr. R. Vi'elch). 



fecondation, as a specimen kept in solitary coufinemeut for three years by 

 Mr. T. Rogers, from August 1875, to July 19th 1878, deposited batches 

 of fertile eggs in August 1S7G, and in July and August of 1877. 



The eggs have been observed to be deposited during July and August, 

 iu clusters of eighteen to tweuty-four, adherent by a mucous-film ; they 

 are very large in comparison with the size of the animal, but vary 

 within certain limits, the largest are more elongate, being eight-and-half 

 by four-and-quarter mill., while the smallest 

 are more regularly oval, and are only six by 

 four mill. AH the eggs when fresh are beauti- 

 ful semitransluccnt milky-white or opalescent, . '''«■ 27i.-ff- macy/osm when 



- ' (• 1 1 1 1 immature, showmg the greater dis- 



hut some 01 the larger ami more elongate ones tinctness of the longitudinal band- 

 show a somewhat transparent area at the '"'s ^'''"" S'^''-'"'^^- 

 smaller end. In a few days the opalescent lustre becomes lost, and the 

 eggs turn yellowish aiid afterwards brown. The young appear to hatch in 

 from six to eight weeks, at which period the spots are barely present, but 

 the lateral banils are distinct and black, and the shield shows the lyre- 



