SYNECHOCOCCUS. 



[ 748 ] 



SYNTETHYS. 



tufted at the end, as long as the frustules 

 are broad. Breadth 1-1150". Found in 

 Peruvian guano. 



BIBL. Ehr. Ber. Bei'l Akad. 1845, 155; 

 Kiitz. Sp. Alg. 141; Pritchard, In/us. 866. 



SYNECH'OCOC'CUS, Nag. A genus of 

 Unicellular Alga3. 



Char. Cells minute, oblong, single or con- 

 joined in rows of 2-4 ; dividing in one di- 

 rection only; endochrome Eeruginous or 

 yellowish. 



S. ceruginosus (PI. 3. fig. 2(1). Common 

 on damp rocks and banks. (Rabenht. Alg. 

 ii. 59.) 



SYNE'DRA, Ehr. A genus of Diato- 

 niacea3. 



Char. Frustules prismatic, rectangular, 

 or curved ; at first attached to a gelatinous, 

 sometimes lobed cushion, subsequently often 

 becoming free; valves linear or lanceolate. 



The valves usually exhibit a longitudinal 

 line, with a dilated median and two termi- 

 nal nodules ; they are also generally covered 

 with transverse strias ; in some species the 

 median line and appearance of a median 

 nodule correspond to a clear space, free 

 from the transverse striaB. 



Species very numerous. 



8. radians, Sm. (splendens, K.) (PI. 17. 

 fig. 23 a, 6, c). Frustules elongated, in front 

 view dilated and truncate at the ends ; 

 valves gradually attenuated from the mid- 

 dle to the obtuse ends. Freshwater ; com- 

 mon; length 1-70". Frustules radiate upon 

 the cushion. 



S. fulgens (Licmophora fulg. K.) (PI. 

 17. fig. 24). Frustules linear ; valves slightly 

 dilated in the middle and at the rounded 

 ends, arranged in a fan-shaped manner upon 

 the branched cushion. Marine ; length 

 1-120". 



S. capitata (PI. 17. fig. 25). Frustules 

 linear, truncate, ends slightly dilated; valves 

 linear, ends dilated into a triangular head. 

 Freshwater ; length 1-60". 



BIBL. Smith, Br. Diat. i. 69; Kiitz. 

 Sp. Alg. 40; Rabenht. Alg. i. 126; Gru- 

 now, M. M. Jn. xviii. 166. 



SYN'GAMUS, Lieb. A genus of Nema- 

 toid Entozoa. S. trachealis is very common 

 in the trachea of poultry, producing the 

 "gapes." (Dujardin, Helminthes, 260; Sie- 

 bold, Wiegmanrfs Arch. 1835; Cobbold, 

 Paras.) 



SYNOVIAL MEMBRANES. In minute 

 structure these resemble serous membranes. 



Synovial membranes are occasionally fur- 

 nished with appendages, some of which 



contain fatty tissue, others abound in capil- 

 laries and form fringes where the synovial 

 membrane is attached to the articular car- 

 tilages. The latter consist of a basis of 

 indistinctly fibrous connective tissue, co- 

 vered by the synovial epithelium, with a 

 few fat-cells, sometimes isolated cartilage- 

 cells, and the capillaries. Attached to their 

 margins are flattened, conical, stalked, 

 smaller appendages (fig. 715), seldom con- 

 taining blood-vessels, and composed of indi- 

 stinctly fibrous areolar tissue, with scattered 

 cartilage-cells, and a thick epithelial layer ; 

 while some of the smaller ones consist 

 almost entirely of epithelial cells or of 

 areolar tissue. 



Fig. 715. 



From he synovial membrane of a finger-joint. 



A. Two appendages of the synovial processes, a, 

 areolar tissue in its axis ; b, epithelium of the free 

 margin : c, that continuous with the epithelium of the 

 processes ; d, cartilage-cells. Magnified 250 diameters. 



S. Four epithelial cells from the synovial membrane 

 of the knee-joiut, one of them with two nuclei. Magni- 

 fied 350 diameters. 



BIBL. Brinton, Todd's Cycl. An. fy Phys. 

 art. Serous Membranes ; Albert, Sti'icker's 

 Hist. iii. 



SYN'TETHYS, Forbes. A genus of 

 Tunicate Mollusca, of the family Botryllidae. 



Char. Mass sessile, gelatinous, forming a 

 single system ; animal sessile, having simple 



