( ( Whereas ( ( ( cyclostomes and ) fishes ) ( only ( have ( ( a ( single envelope ) ) ( called ( the ( primitive meninx ) ) ) ) ) ) ) ) ( , ( amphibians ( ( have ( ( ( ( ( ( two layers ) , ) ( consisting ( of ( ( an ( outer ( dura mater ) ) ) ( which ( is ( extremely ( ( dense and ) protective ) ) ) ) ) ) ) ) , ) and ) ( ( a ( pia-arachnoid ( or ( secondary meninx ) ) ) ) ( which ( is ( more ( ( delicate and ) vascular ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Whereas) (S (NP (NNS cyclostomes) (CC and) (NNS fishes)) (ADVP (RB only)) (VP (VBP have) (NP (NP (DT a) (JJ single) (NN envelope)) (VP (VBN called) (NP (DT the) (JJ primitive) (NN meninx))))))) (, ,) (NP (NNS amphibians)) (VP (VBP have) (NP (NP (CD two) (NNS layers)) (, ,) (VP (VBG consisting) (PP (IN of) (NP (NP (DT an) (JJ outer) (NN dura) (NN mater)) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADJP (RB extremely) (JJ dense) (CC and) (JJ protective)))))))) (, ,) (CC and) (NP (NP (DT a) (JJ pia-arachnoid) (CC or) (JJ secondary) (NN meninx)) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADJP (RBR more) (JJ delicate) (CC and) (JJ vascular)))))))) (. .)))
Whereas cyclostomes and fishes only have a single envelope called the primitive meninx, amphibians have two layers, consisting of an outer dura mater which is extremely dense and protective, and a pia-arachnoid or secondary meninx which is more delicate and vascular.
(ROOT (S (NP (NP (DT The) (CD three) (NNS layers)) (PP (IN of) (NP (NP (JJ protective) (NNS coverings)) (PP (IN of) (NP (DT the) (JJ spinal) (NN cord)))))) (VP (VBZ is) (VP (VBN called) (NP (DT the) (NNS meninges)))) (. .)))