REPORT ON THE RADIOLARIA. 617 



Subfamily 1. LAKNACILLIDA, Haeckel. 



Definition. L arnacida with a simple, spherical or lentelliptical, medullary 

 shell, connected by the lateral wings of a latticed transverse girdle with the simple 

 lentelliptical trizonal cortical shell ; the central capsule encloses the former and is 

 enveloped by the latter. 



Genus 272. Larnacilla? n. gen. 



Definition. L arnacida with a simple lentelliptical cortical shell, connected by 

 the lateral wings of a latticed transverse girdle with the simple, spherical or lentelliptical, 

 medullary shell. Surface without radial spines. 



The genus Larnacilla represents the most simple form of Larnacicla, and at the 

 same time the most important common ancestral form, from which the greater number 

 of Larcoidea may be derived, viz., all those genera which possess the characteristic 

 " Larnacilla -shaped medullary shell." This typical form of medullary shell may be 

 derived from the genus Trizonium among the Pylonida by the closing of the four 

 open gates of this genus. The free opening of these four gates becomes overgrown and 

 closed by lattice-work, developed from the free edges of the three crossed girdles, and 

 thus finally all three girdles are united in the form of a simple lentelliptical shell 

 (PI. 5O, figs. 1, la, 16). Seen from the sagittal poles (or from the poles of the 

 shortest axis, fig. 1), the shell exhibits on both sides of the small spherical medullary 

 shell the two lateral wings of the transverse girdle from the face ; seen from the lateral 

 poles (or from the poles of the transverse axis, fig. la), one of these wings appears in the 

 optical section as an oblong ring, which seemingly encloses the concentric medullary 

 shell, and on both sides is grown together with the sagittal girdle ; seen from the 

 principal poles (or from the poles of the longitudinal axis, fig. Ib), both wings exhibit 

 their elliptical opening (at the right and left from the central medullary shell). The 

 two concentric shells are only connected by the two lateral tube-like wings of the trans- 

 verse girdle ; the lateral and the sagittal girdles have no connection with the medullary 

 shell. The latter is sometimes spherical, at other times lentelliptical. 



1. Larnacilla typus, n. sp. (PL 50, fig. 1, la, 16). 



Cortical shell with smooth surface and with subregular network ; pores twice as broad as 

 the bars ; about twelve pores on the half meridian, ten on the half equator. Proportion of the 

 three dimensive axes = 2:3:4. Internal four gates (between transverse and lateral girdles) roundish- 

 triangular, little broader than high. Medullary shell spherical, scarcely one-third as broad as the 

 lentelliptical cortical shell. 



1 Larnacilla = Little chest, diminutive of Larnax ; hdrua.!-. 



(ZOOL. CHALL. EXP. PART XL. 1885.) Rr 78 



